CVE-2026-8445: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in EmilStenstrom justhtml
Description
justhtml versions up to 1.11.0 have a cross-site scripting (XSS) vulnerability due to insufficient escaping of HTML-significant characters in Markdown output. This allows untrusted input containing entity-decoded text or content from certain HTML elements to be emitted as raw HTML, potentially bypassing sanitizers and enabling XSS when rendered. The issue is fixed in version 1.12.0.
CVSS v4.0
Score 9.3critical
Affected software
EmilStenstrom
justhtml
pkg:github/emilstenstrom/justhtmlRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in justhtml (<=1.11.0) arises from improper neutralization of input during web page generation in the to_markdown() function. While some Markdown metacharacters are escaped, angle brackets (< and >) are not, allowing entity-decoded text or text from RCDATA/RAWTEXT elements (e.g., <title>, <textarea>, <noscript>, <plaintext>) to be output as raw HTML. This can lead to a sanitizer bypass and cross-site scripting when the Markdown output is rendered. The flaw is addressed in version 1.12.0.
Potential Impact
An attacker can inject malicious HTML or script code via untrusted input that is not properly escaped in Markdown output, leading to cross-site scripting (XSS). This can result in execution of arbitrary scripts in the context of the victim's browser, potentially compromising user data or session integrity. The CVSS 4.0 score is 9.3 (critical), indicating high impact with no required privileges or user interaction.
Mitigation Recommendations
Upgrade justhtml to version 1.12.0 or later, where the vulnerability is fixed by properly escaping HTML-significant characters in the to_markdown() output. No other mitigation guidance is provided; patching is the recommended action.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-05-12T20:21:38.368Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a8afb27acd9273b49f5f72f
Added to database: 08/23/2026, 13:52:39 UTC
Last enriched: 09/10/2026, 12:52:38 UTC
Last updated: 10/06/2026, 06:48:21 UTC
Views: 162
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