Security Review
jewbetcha/opentrace
A skill your agent uses when adding authentication, handling user input, working with secrets, creating API endpoints, or implementing payment/sensitive features.
A skill your agent uses when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based…
Install Token Storage Security
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-security --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/token-storage-security .claude/skills/token-storage-security && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .claude/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-securityType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-security --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/token-storage-security .agents/skills/token-storage-security && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .agents/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-security --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/token-storage-security .cursor/skills/token-storage-security && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .cursor/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/thedaviddias/Front-End-Checklist.git --path skills/token-storage-security--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-security --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/token-storage-security .gemini/skills/token-storage-security && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .gemini/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-securityInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/token-storage-security .github/skills/token-storage-security && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .github/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install thedaviddias/Front-End-Checklist token-storage-security --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/token-storage-security .opencode/skills/token-storage-security && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "token-storage-security" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/token-storage-security into .opencode/skills/token-storage-security/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "token-storage-security", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
token-storage-security- GitHub stars
- 74k
- Token cost
- ~604 tokens
- SKILL.md length
- 261 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based…
- Reviewing authentication implementation
- SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Setting up a new auth system
What it does
Token Storage Security is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based token theft.
Its SKILL.md is about 600 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).
It sits in Security, covering Web application vulnerabilities and Authentication. It works with JavaScript. The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.
When your agent uses it
- Reviewing authentication implementation
- Setting up a new auth system
- Evaluating whether the current token storage approach exposes the application to XSS-based token theft
Example prompts
- “/token-storage-security”
What it can do on your machine
Read from SKILL.md and the folder at commit e8d14d0. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
frontendchecklist.io
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Token Storage Security loads about 604 tokens when it runs, and up to ~2.8k if it reads all its reference files. Until then it costs about 52 tokens; SKILL.md has 261 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 261 words, ~604 tokens.
Download SKILL.mdSave it as
.claude/skills/token-storage-security/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- token-storage-security
- description
- Use when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based token theft.
- metadata.category
- security
- metadata.priority
- high
- metadata.difficulty
- intermediate
- metadata.estimatedTime
- 30
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/security/token-storage-security
Store authentication tokens securely
localStorage is accessible to any JavaScript running on the page. A single XSS vulnerability — including one in a third-party script — can exfiltrate all tokens silently. httpOnly cookies are completely invisible to JavaScript; even if an attacker executes arbitrary code on the page, they cannot read the cookie. This single architectural choice eliminates the most common token theft vector.
Quick Reference
- Store session tokens and JWTs in httpOnly cookies — not localStorage
- localStorage is readable by any JavaScript on the page, including injected XSS code
- Combine httpOnly with Secure and SameSite=Strict (or Lax) cookie flags
- Use short-lived access tokens and rotate refresh tokens on each use
- Protect every state-changing request with CSRF defenses, not cookie flags alone
Check
Check whether authentication tokens are stored in httpOnly cookies or in JavaScript-accessible storage like localStorage. Verify that POST, PUT, PATCH, and DELETE requests also require a CSRF token or an equivalent anti-forgery control.
Fix
Move token storage from localStorage/sessionStorage to httpOnly cookies set by the server, and ensure the cookies have Secure and SameSite flags. Add CSRF protection to every state-changing route that relies on browser-sent credentials.
Explain
Explain why localStorage is vulnerable to XSS token theft and how httpOnly cookies mitigate this attack vector.
Code Review
Review authentication flows, token storage calls, and API client code. Flag any use of localStorage.setItem, sessionStorage.setItem, or document.cookie for storing access tokens, JWTs, or session identifiers. Also flag credentialed mutations that lack a CSRF token, Origin check, or same-site enforcement.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/security/token-storage-security
© thedaviddias, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/token-storage-security of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Token Storage Security next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Token Storage Security this skillthedaviddias/Front-End-Checklist | 74k | — | ~604 | Automated safety check: Pass | MIT | |
| Security Reviewjewbetcha/opentrace | 116 | 18 repos | ~3.1k | Automated safety check: Notes | MIT | |
| API Security Checklistrevfactory/harness-100 | 1.3k | — | ~1.7k | Automated safety check: Pass | Apache-2.0 | |
| Secure Code GuardianJeffallan/claude-skills | 12k | — | ~1.8k | Automated safety check: Pass | MIT | |
| Exploiting Prototype Pollution In Javascriptmukul975/Anthropic-Cybersecurity-Skills | 34k | — | ~2.3k | Automated safety check: Pass | Apache-2.0 | |
| Defending Applicationstelagod/code-abyss | 243 | — | ~777 | Automated safety check: Pass | MIT |
Similar skills
API Security Checklist
revfactory/harness-100
Walks a backend-dev agent through OWASP API Top 10 checks, authentication and authorization patterns, and defense code during API design.
Secure Code Guardian
Jeffallan/claude-skills
Guides secure implementation of authentication, authorization, input validation and security headers, with password hashing, parameterized queries and OWASP Top 10 checks.
Exploiting Prototype Pollution In Javascript
mukul975/Anthropic-Cybersecurity-Skills
Detects and exploits JavaScript prototype pollution vulnerabilities in client-side and server-side (Node.js) applications to achieve XSS, RCE, or authentication bypass through property injection…
Defending Applications
telagod/code-abyss
Application security defense knowledge for builders. An agent skill from telagod/code-abyss.
Performing API Inventory And Discovery
mukul975/Anthropic-Cybersecurity-Skills
Performs API inventory and discovery to identify all API endpoints in an organization's environment including documented, undocumented, shadow, zombie, and deprecated APIs.
More from thedaviddias/Front-End-Checklist
All 390 skills in this repoContent Dates Audit
thedaviddias/Front-End-Checklist
Audits article and blog pages for visible publish dates, Article JSON-LD with datePublished and dateModified, and Open Graph time tags, then fixes what is missing.
FAQPage Schema Markup
thedaviddias/Front-End-Checklist
Adds, checks and fixes FAQPage JSON-LD on pages with visible question-and-answer sections so it matches what readers see and can qualify for rich results.
Favicon Audit and Setup
thedaviddias/Front-End-Checklist
Checks that a site's favicon is linked, reachable and large enough for Google search results, and sets up ICO, SVG and Apple touch icon files when they are missing.
Content Freshness Signals
thedaviddias/Front-End-Checklist
Audits article pages for freshness signals, covering the Last-Modified header, Article JSON-LD dateModified and a visible last-updated date, and fixes mismatches.
Geo Meta Tags Audit
thedaviddias/Front-End-Checklist
Audits and fixes geo.region, geo.placename and geo.position meta tags on regional pages, noting where they help (Bing) and where they do not (Google).
Improve a Front-End Checklist Rule
thedaviddias/Front-End-Checklist
Scores and rewrites a Front-End Checklist rule MDX file against a scored quality rubric, replacing generic stub prompts with specific, actionable ones.
Related
Works with
Categories
Questions about Token Storage Security
What does Token Storage Security do?
A skill your agent uses when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based…. Token Storage Security is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing authentication implementation, setting up a new auth system, or evaluating whether the current token storage approach exposes the application to XSS-based token theft.
When should I use Token Storage Security?
Token Storage Security fits situations like: reviewing authentication implementation; setting up a new auth system; evaluating whether the current token storage approach exposes the application to XSS-based token theft.
How do I install Token Storage Security in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a claude-code`. Or copy the skill folder (skills/token-storage-security in thedaviddias/Front-End-Checklist) into .claude/skills/token-storage-security in your project. Claude Code loads it when a task matches its description.
How do I install Token Storage Security in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a codex`. Or copy the skill folder (skills/token-storage-security in thedaviddias/Front-End-Checklist) into .agents/skills/token-storage-security in your project. Codex loads it when a task matches its description.
Can I use Token Storage Security in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add thedaviddias/Front-End-Checklist --skill token-storage-security -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/token-storage-security, .gemini/skills/token-storage-security, .github/skills/token-storage-security and .opencode/skills/token-storage-security in your project.
What does Token Storage Security need to run?
SKILL.md names no scripts, command-line tools or credentials: Token Storage Security is instructions for the agent only.
Does Token Storage Security access the network?
SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.
Is Token Storage Security safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Token Storage Security use?
Token Storage Security is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Token Storage Security use?
About 604 tokens (SKILL.md is roughly 2.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 2.2k tokens, read only when the agent opens those files.
What are the alternatives to Token Storage Security?
Skills that share tags, products or a category with Token Storage Security: Security Review (jewbetcha/opentrace, 116 stars), API Security Checklist (revfactory/harness-100, 1.3k stars), Secure Code Guardian (Jeffallan/claude-skills, 12k stars) and Exploiting Prototype Pollution In Javascript (mukul975/Anthropic-Cybersecurity-Skills, 34k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Token Storage Security?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,412 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.
Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.