CVE-2026-10513 Webmention <= 5.8.0 - Unauthenticated Stored Cross-Site Scripting via MF2 'photo'/'url' Author Properties
Unauthenticated attackers can inject scripts via webmention author properties, executing them when admins view comment edit screens.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-10513?
CVE-2026-10513 is a high-severity cross-site scripting vulnerability in pfefferle Webmention, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The Webmention plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to and including 5.8.0 via parser-derived 'avatar' and 'url' author metadata. This is due to insufficient input sanitization and output escaping on user-supplied MF2 author properties processed by the unauthenticated webmention REST endpoint and rendered directly into HTML 'value' attributes by the edit-comment-form template without esc_attr() or esc_url(). This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a privileged user (moderator or administrator) opens the affected comment edit screen.
Weakness: CWE-79
Which versions are affected by CVE-2026-10513?
How do I fix CVE-2026-10513?
No fix has been published for CVE-2026-10513 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-10513 being exploited?
There is no known exploitation of CVE-2026-10513 in the wild and no public exploit code.
Sources
Also known as GHSA-q4c4-6mqr-j8hq.