How the Mentioned CVE Works:
The vulnerability in JS Html Sanitizer (CVE-2025-XXXX) arises when the sanitizer is used in conjunction with a `contentEditable` element. The issue occurs when the `innerHTML` of the element is set to a sanitized string produced by the package. Despite the sanitization process, a specially crafted payload can bypass the sanitizer due to the interaction with a code beautifier that runs after sanitation. This allows an attacker to inject malicious scripts, leading to Cross-Site Scripting (XSS) attacks. The vulnerability is particularly dangerous in applications where user-generated content is displayed without additional security measures.
DailyCVE Form:
Platform: JS Html Sanitizer
Version: < 2.0.3
Vulnerability: XSS Bypass
Severity: Moderate
Date: Mar 14, 2025
What Undercode Say:
Exploitation:
- Payload Crafting: Attackers can craft malicious HTML or JavaScript payloads that exploit the sanitizer’s interaction with the code beautifier.
- ContentEditable Abuse: By injecting payloads into `contentEditable` elements, attackers can execute scripts in the context of the victim’s browser.
3. Example Payload: `
`.
Protection:
- Update: Upgrade to version 2.0.3 or later, which includes patches for this vulnerability.
- Input Validation: Implement strict input validation to ensure no malicious content is processed.
- Output Encoding: Use output encoding libraries to sanitize user-generated content before rendering.
- Content Security Policy (CSP): Enforce a strict CSP to mitigate the impact of XSS attacks.
Commands:
1. Check Version: `npm list js-html-sanitizer`
2. Update Package: `npm install [email protected]`
3. CSP Header: `Content-Security-Policy: default-src ‘self’; script-src ‘self’;`
Code Snippets:
1. Sanitization Fix:
const sanitizer = require('js-html-sanitizer');
const sanitizedHTML = sanitizer.sanitize(userInput);
element.innerHTML = sanitizedHTML;
2. CSP Implementation:
<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self';">
3. Input Validation:
function validateInput(input) {
const regex = /<script.?>.?<\/script>/gi;
return input.replace(regex, '');
}
4. Output Encoding:
const he = require('he');
const safeOutput = he.encode(userInput);
Analytics:
- Affected Users: Applications using JS Html Sanitizer versions below 2.0.3 with `contentEditable` elements.
- Risk Level: Moderate, due to the potential for XSS attacks.
- Patch Adoption: Critical for developers to update immediately to prevent exploitation.
By following these steps, developers can mitigate the risks associated with CVE-2025-XXXX and ensure their applications remain secure.
References:
Reported By: https://github.com/advisories/GHSA-vhv4-fh94-jm5x
Extra Source Hub:
Undercode
