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An open-source analysis tool to detect vulnerabilities in code is Semgrep. You can configure your own detection rules or use rules created by the community.
Dangerous JavaScript Functions and Properties:
– `Element.innerHTML`
– `eval()`
– `window.postMessage()`
– `window.addEventListener()`
– `window.localStorage`
– `window.sessionStorage`
– `document.cookie`
You Should Know:
1. Using Semgrep for Static Code Analysis
Install Semgrep and scan JavaScript files for dangerous patterns:
pip install semgrep semgrep --config=p/javascript.best-practice dangerous-functions.js
2. Detecting `eval()` and `innerHTML` Misuse
Create a custom Semgrep rule (`dangerous-functions.yaml`):
rules: - id: dangerous-eval pattern: eval(...) message: "Avoid eval() due to XSS risks" severity: ERROR - id: unsafe-innerhtml pattern: document.innerHTML = ... message: "Unsafe innerHTML usage detected" severity: WARNING
Run the scan:
semgrep --config=dangerous-functions.yaml your_code.js
3. Mitigating `postMessage` Security Risks
Always validate message origins:
window.addEventListener("message", (event) => {
if (event.origin !== "https://trusted-site.com") return;
// Process message
});
4. Securing `localStorage` and `sessionStorage`
Avoid storing sensitive data:
Check for exposed storage in browser console console.log(localStorage);
5. Auditing `document.cookie` for Security Flags
Ensure cookies have:
Secure; HttpOnly; SameSite=Strict
Check cookies via:
curl -I http://example.com | grep -i set-cookie
What Undercode Say:
Static analysis tools like Semgrep help identify risky JavaScript functions before deployment. Always sanitize inputs, avoid eval(), and enforce strict CSP headers. For secure coding, combine automated scanning with manual code reviews.
Expected Output:
┌─────────────┬──────────────┬───────────┐ │ File │ Vulnerability │ Severity │ ├─────────────┼──────────────┼───────────┤ │ script.js │ eval() │ ERROR │ │ index.html │ innerHTML │ WARNING │ └─────────────┴──────────────┴───────────┘
Prediction:
Increased adoption of AI-powered static analyzers will reduce XSS vulnerabilities in JavaScript by 40% in 2025.
Relevant URLs:
References:
Reported By: Sarveshkumar0 Infosec – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
