CVE-2026-126498 WriteFreely before 0.17.3 Stored XSS via Unsanitized Post Slug
Authenticated authors can store script in a post slug that runs for RSS, newsletter and ActivityPub readers; WriteFreely operators should care.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Harmful if only installed
- No
- Needs a specific call
- No
- Fix
- None listed
What is CVE-2026-126498?
CVE-2026-126498 is a medium-severity cross-site scripting vulnerability in Musing Studio WriteFreely, published on 11 Nov 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
WriteFreely before 0.17.3 contains a stored cross-site scripting vulnerability that allows authenticated authors to inject HTML by supplying a malicious post slug via the CreatePost API. The raw slug is concatenated into an anchor by augmentReadingDestination() for paid-shortcode posts, executing script for RSS/Atom feed readers, newsletter recipients and ActivityPub viewers.
Weakness: CWE-79
Which versions are affected by CVE-2026-126498?
An affected version is exposed as installed. No special setting or call is needed.
How do I fix CVE-2026-126498?
No fix has been published for CVE-2026-126498 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-2026-126498 being exploited?
There is no known exploitation of CVE-2026-126498 in the wild and no public exploit code.
Sources
Also known as GHSA-43p2-x762-x6h7, GHSA-cwxm-8ch5-j2vh.