AVideo - Incomplete Fix for CVE-2026-27568: Stored XSS via Markdown javascript: URI Bypasses ParsedownSafeWithLinks Sanitization

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.4 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-33500: 0.23% estimated exploitation activity in the next 30 days; percentile 13.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom ParsedownSafeWithLinks class that sanitizes raw HTML <a and <img tags in comments, but explicitly disables Parsedown's safeMode. This creates a bypass: markdown link syntax text) is processed by Parsedown's inlineLink() method, which does not go through the custom sanitizeATag() sanitization (that only handles raw HTML tags). With safeMode disabled, Parsedown's built-in javascript: URI filtering (sanitiseElement()/filterUnsafeUrlInAttribute()) is also inactive. An attacker can inject stored XSS via comment markdown links. Details The original fix (commit ade348ed6) enabled setSafeMode(true), which activated Parsedown's built-in URL scheme filtering. This was then replaced by commit f13587c59 with a custom approach that turned safeMode back off: objects/functionsSecurity.php:442-446 — safeMode disabled: ParsedownSafeWithLinks (lines 349-440) overrides blockMarkup() and inlineMarkup() to sanitize raw HTML <a…

Published by the source

20 Mar 2026, 20:56 UTC

Last modified by the source

25 Mar 2026, 20:31 UTC

Source last checked

26 Oct 2026, 14:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-72h5-39r7-r26j

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# Patch Next advisory brief: CVE-2026-33500

Advisory: AVideo - Incomplete Fix for CVE-2026-27568: Stored XSS via Markdown `javascript:` URI Bypasses ParsedownSafeWithLinks Sanitization
IDs: CVE-2026-33500, GHSA-72h5-39r7-r26j
Record: https://patchnext.com/advisories/cve-2026-33500 (revision 1, source checked 26 Oct 2026, 14:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist wwbn/avideo: affected <= 26.0

## Suggested inspection (read-only)
- Packagist wwbn/avideo: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on wwbn/avideo.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-72h5-39r7-r26j (GitHub-reviewed advisory GHSA-72h5-39r7-r26j lists affected ranges: Packagist wwbn/avideo >=0 <=26.0)

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