javascript-injection

A JavaScript and TypeScript security rule that detects code patterns linked to injection attacks, where user input can become executable code or HTML.

In plain words
What is it for?
Use it while reviewing JavaScript, JSX, or TypeScript files for code injection and cross-site scripting risks.
Why use it?
It flags unsafe uses of functions such as eval and jQuery HTML insertion before attackers can exploit them.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/abderrahimghazali/cursor-rules/javascript-injection
Clone the repo
git clone --depth 1 https://github.com/abderrahimghazali/cursor-rules

Made for: Cursor.

Per session 1,984 This file is loaded in full into every session.
When invoked 1,984 The same file — it is already loaded in full.
Security scan A 2 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.01984 $0.01984
Opus 5 $0.00992 $0.00992
Sonnet 5 $0.00397 $0.00397
Haiku 4.5 $0.00198 $0.00198

Measured yesterday against content hash 2320cdbcffa0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

javascript-injection 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 yesterday.

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.

Impact: Attackers can execute arbitrary code in your application context.

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

// Use child_process.execFile with separate arguments
Origin

This is a copy

100% identical to javascript-injection — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.cursor/rules/javascript-injection.mdc · 217 lines

How it starts

The opening of the file, as written. The whole thing — 217 lines — stays where its author put it; the contents beside it link to each section on GitHub.


description: Identifies and helps prevent injection vulnerabilities in JavaScript applications, as defined in OWASP Top 10:2021-A03. globs: /.js, **/.jsx, /.ts, **/.tsx, !/node_modules/, !/dist/, !/build/, !/coverage/

JavaScript Injection Security Rule

actions:

  • type: enforce conditions:
    • pattern: "eval\(([^)](req|request|query|param|user|input)[^)])\)" severity: "critical" message: | 🔴 CRITICAL: Potential code injection vulnerability detected.

      Impact: Attackers can execute arbitrary code in your application context. CWE Reference: CWE-95 (Improper Neutralization of Directives in Dynamically Evaluated Code)

      ❌ Insecure: eval(req.body.data)

      ✅ Secure Alternative: // Use safer alternatives like JSON.parse for JSON data try { const data = JSON.parse(req.body.data); // Process data safely } catch (error) { // Handle parsing errors } learn_more_url: "https://owasp.org/www-community/attacks/Direct_Dynamic_Code_Evaluation_Eval_Injection"

    • pattern: "\$\(\s*(['"])<[^>]+>\1\s*\)" severity: "high" message: | 🟠 HIGH: jQuery HTML injection vulnerability detected.

      Impact: This can lead to Cross-Site Scripting (XSS) attacks. CWE Reference: CWE-79 (Improper Neutralization of Input During Web Page Generation)

      ❌ Insecure: $("" + userProvidedData + "")

      ✅ Secure Alternative: // Create element safely, then set text content const div = $(""); div.text(userProvidedData); learn_more_url: "https://cheatsheetseries.owasp.org/cheatsheets/jQuery_Security_Cheat_Sheet.html"

    • pattern: "document\.write\(|document\.writeln\(" severity: "high" message: | 🟠 HIGH: Potential DOM-based XSS vulnerability.

      Impact: Attackers can inject malicious HTML/JavaScript into your page. CWE Reference: CWE-79 (Improper Neutralization of Input During Web Page Generation)

      ❌ Insecure: document.write("" + userGeneratedContent + "");

      ✅ Secure Alternative: // Use safer DOM manipulation methods const h1 = document.createElement("h1"); h1.textContent = userGeneratedContent; document.body.appendChild(h1); learn_more_url: "https://cheatsheetseries.owasp.org/cheatsheets/DOM_based_XSS_Prevention_Cheat_Sheet.html"

    • pattern: "innerHTML\s*=|outerHTML\s*=" pattern_negate: "sanitize|DOMPurify|escapeHTML" severity: "high" message: | 🟠 HIGH: Potential DOM-based XSS through innerHTML/outerHTML.

      Impact: Setting HTML content directly can allow script injection. CWE Reference: CWE-79 (Improper Neutralization of Input During Web Page Generation)

      ❌ Insecure: element.innerHTML = userProvidedData;

      ✅ Secure Alternative: // Option 1: Use textContent instead for text element.textContent = userProvidedData;

      // Option 2: Sanitize if HTML is required import DOMPurify from 'dompurify'; element.innerHTML = DOMPurify.sanitize(userProvidedData); learn_more_url: "https://cheatsheetseries.owasp.org/cheatsheets/DOM_based_XSS_Prevention_Cheat_Sheet.html"

    • pattern: "\$\(.*\)\.html\(" pattern_negate: "sanitize|DOMPurify|escapeHTML" severity: "high" message: | 🟠 HIGH: jQuery HTML injection risk detected.

Read the full file on GitHub · 217 lines

Changes

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.

  1. yesterday First seen · 217 lines · 1,984 tokens per session scan A 2320cdbcffa0

Subscribe to this mod's changes

javascript-injection is a cursor rule published in the GitHub repository abderrahimghazali/cursor-rules (2 stars, last pushed 1y ago), licensed MIT. It adds 1,984 tokens to every session, about $0.0099 per session on Opus 5. A static security scan graded it A with 2 findings (unrestricted tool access, runs shell commands). It is 100% identical to javascript-injection, differing in 0 lines, and is treated as a copy.