CVE-2026-121863 Knowledge Building < 0.7.3 - Reflected XSS via Comment Reply Response
Unauthenticated attackers can craft links that run scripts in victims' browsers via an unescaped AJAX response in the Knowledge Building WordPress plugin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- 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-2026-121863?
CVE-2026-121863 is a high-severity cross-site scripting vulnerability in Unknown Knowledge Building, published on 11 Nov 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
The Knowledge Building WordPress plugin before 0.7.3 does not escape several user-supplied values before echoing them back in the response of an AJAX action available to unauthenticated users, and serves that response as HTML, leading to a Reflected Cross-Site Scripting.
Weakness: CWE-79
Which versions are affected by CVE-2026-121863?
An affected version is exposed as installed. No special setting or call is needed.
How do I fix CVE-2026-121863?
No fix has been published for CVE-2026-121863 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-2026-121863 being exploited?
There is no known exploitation of CVE-2026-121863 in the wild and no public exploit code.
Sources
Also known as GHSA-5542-wp67-24rf.