SAST Skills is a collection of agent workflows that inspect web and mobile application code for security vulnerabilities, where SAST means static application security testing. Developers and security reviewers use it to map a codebase, verify possible flaws, and produce a severity-ranked remediation report. The catalogue entries are the project's vulnerability-detection and reporting skills.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add utkusen/sast-skills --skill sast-xssgit clone --depth 1 https://github.com/utkusen/sast-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/utkusen/sast-skills/sast-xss)<a href="https://agentmods.dev/skills/utkusen/sast-skills/sast-xss"><img src="https://agentmods.dev/badge/skills/utkusen/sast-skills/sast-xss/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/utkusen/sast-skills/sast-xss"><img src="https://agentmods.dev/badge/skills/utkusen/sast-skills/sast-xss.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 10 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Output Handling · line 55 Model output is used without validation or sanitization. Unvalidated output injected into downstream contexts (SQL, shell, HTML) enables injection attacks and arbitrary code execution.Fix: Validate and sanitize all model output before using it in downstream contexts. Use parameterized queries for SQL, shell quoting for commands, and HTML encoding for web output.
- high Output Handling · line 285 Model output is used without validation or sanitization. Unvalidated output injected into downstream contexts (SQL, shell, HTML) enables injection attacks and arbitrary code execution.Fix: Validate and sanitize all model output before using it in downstream contexts. Use parameterized queries for SQL, shell quoting for commands, and HTML encoding for web output.
- high Output Handling · line 395 Model output is used without validation or sanitization. Unvalidated output injected into downstream contexts (SQL, shell, HTML) enables injection attacks and arbitrary code execution.Fix: Validate and sanitize all model output before using it in downstream contexts. Use parameterized queries for SQL, shell quoting for commands, and HTML encoding for web output.
- high Prompt Injection · line 157 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
- high Prompt Injection · line 241 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
- medium Excessive Agency · line 22 Skill grants unrestricted tool access without appropriate constraints. An agent with unfettered tool access can perform arbitrary actions including file modification, network requests, and code execution.Fix: Restrict tool access to only the tools required for the skill's stated purpose. Use an explicit allowlist rather than granting blanket access.
- medium Tool Misuse · line 56 Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
- medium Tool Misuse · line 300 Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
- medium Tool Misuse · line 396 Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
- medium Tool Misuse · line 619 Tool defaults are unsafe or overly permissive (e.g. disabled TLS verification, no authentication, world-writable permissions). Unsafe defaults widen the attack surface.Fix: Override unsafe defaults with secure settings (verify=True, auth required, restrictive permissions). Review and harden all tool configurations.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00099 | $0.07607 |
| Opus 5 | $0.00049 | $0.03803 |
| Sonnet 5 | $0.00020 | $0.01521 |
| Haiku 4.5 | $0.00010 | $0.00761 |
Grade A, and why
sast-xss scanned grade A with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 13d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Unrestricted tool accesslowExcessive agency
A wildcard tool grant or "run any command" leaves no least-privilege boundary at all.
XSS occurs when user-supplied input is incorporated into a web page's HTML, JavaScript, or DOM without proper escaping or sanitization. This allows attackers to inject and execute arbitrary scripts in victims' browsers, Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
> [curl command or browser payload to confirm the finding. How it starts
The opening of the file, as written. The whole thing — 622 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Cross-Site Scripting (XSS) Detection
You are performing a focused security assessment to find Cross-Site Scripting vulnerabilities in a codebase. This skill uses a three-phase approach with subagents: recon (find sink sites), batched verify (trace taint for parallel batches of up to 3 sinks each), and merge (consolidate batch results into one report).
Prerequisites: sast/architecture.md must exist. Run the analysis skill first if it doesn't.
What is XSS
XSS occurs when user-supplied input is incorporated into a web page's HTML, JavaScript, or DOM without proper escaping or sanitization. This allows attackers to inject and execute arbitrary scripts in victims' browsers, leading to session hijacking, credential theft, defacement, and malware distribution.
The core pattern: unescaped, unsanitized user input reaches an HTML/JS output sink.
XSS Types
- Reflected XSS: User input is immediately echoed back in the HTTP response (e.g., a search term rendered directly into the page HTML).
- Stored XSS: User input is saved to persistent storage (database, file) and later rendered in HTML for other users.
- DOM-based XSS: Client-side JavaScript reads from an attacker-controlled source (
location.search,location.hash,document.cookie) and writes to a dangerous DOM sink (innerHTML,eval,document.write) without server involvement.
What XSS IS
Server-side HTML sinks — rendering user data into HTML responses without escaping:
- Python/Jinja2:
{{ var | safe }},{% autoescape off %}...{{ var }}...{% endautoescape %} - Python/Django:
mark_safe(var),format_html(...)with%sand unescaped input,{{ var | safe }}in templates - Python/Flask:
Markup(var),render_template_string(f"...{var}...") - PHP:
echo $var,print $var,<?= $var ?>withouthtmlspecialchars() - Ruby/Rails:
raw(var),var.html_safe,<%= raw var %>,content_tagwith.html_safe - Java/JSP:
<%= var %>,${var}without<c:out>orfn:escapeXml() - Java/Thymeleaf:
th:utext="${var}"(unescaped),[(${var})] - Go/html-template misuse: using
template.HTML(var),template.JS(var),template.URL(var)to bypass auto-escaping - C#/Razor:
@Html.Raw(var),MvcHtmlString.Create(var) - Node.js/EJS:
<%- var %>(unescaped), vs<%= var %>(safe) - Node.js/Handlebars:
{{{ var }}}(triple-brace, unescaped) - Node.js/Pug:
!{var}(unescaped) - Express:
res.send("<html>..." + var + "..."),res.write("<p>" + var + "</p>")
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 13d ago First seen · 622 lines · 99 tokens per session scan A 034e4f5770d8
sast-xss is a skill published in the GitHub repository utkusen/sast-skills (1,309 stars, last pushed 5mo ago), licensed MIT. It adds 99 tokens to every session and 7,607 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 2 findings (unrestricted tool access, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
secure-code-review
Performs a structured security code review against OWASP ASVS 4.0.3 verification requirements and CWE Top 25. Auto-invoked on pull request reviews, when code touching authentication, authorization, cryptography, or input handling is shared. Produces findings mapped to ASVS controls and CWE identifiers with severity…
sast-config
Reviews and tunes SAST tool configurations against OWASP ASVS 4.0.3 and CWE Top 25. Auto-invoked when reviewing Semgrep rules, CodeQL queries, SAST CI integration, or false positive triage workflows. Produces a SAST maturity assessment covering rule authoring, severity tuning, custom rule development, and CI…
eresus-manual-security-audit
Elite manual security code review skill for deep, adversarial vulnerability hunting and exploit-chain discovery. Trigger when the user asks to: "do a deep security audit", "manual code review", "find exploit chains", "hunt for logic bugs", "red-team this codebase", "do an offensive security review", "review this like…
eresus-php-audit
Deep PHP-specific security audit skill covering injection, deserialization, file operations, auth bypass, POP chain discovery, and CMS-specific patterns. Trigger when auditing PHP code: "audit this PHP app", "find PHP security issues", "check Laravel/WordPress for vulnerabilities", "PHP SAST review", "check for PHP…
eresus-sast-scanner
General-purpose Static Application Security Testing (SAST) skill for code vulnerability analysis. Trigger when the user asks to: "analyze code for vulnerabilities", "review code security", "find security bugs", "do a SAST scan", "check for [vulnerability type] in code", "audit source code", or requests a security code…
eresus-python-audit
Deep Python-specific security audit skill with 50+ vulnerability class coverage across 7 categories. Trigger when auditing Python code: "audit this Python app", "find Python security issues", "check Flask/Django for vulnerabilities", "Python SAST review", "check for pickle vulnerabilities", "review this FastAPI code".…