CVE-2026-78438 W3 Total Cache <= 2.10.5 - Unauthenticated Stored Cross-Site Scripting via LazyLoad Background Mutator
Unauthenticated attackers can inject arbitrary scripts via comments in W3 Total Cache if Lazy Load background images are enabled, leading to script execution.
- 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-2026-78438?
CVE-2026-78438 is a high-severity cross-site scripting vulnerability in boldgrid W3 Total Cache, published on 5 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The W3 Total Cache plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Content via LazyLoad Background Mutator in all versions up to, and including, 2.10.5 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the "Lazy Load Images" feature with "Process background images" to be enabled, and the malicious comment to be approved by a moderator before execution is triggered.
Weakness: CWE-79
Which versions are affected by CVE-2026-78438?
How do I fix CVE-2026-78438?
No fix has been published for CVE-2026-78438 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-2026-78438 being exploited?
There is no known exploitation of CVE-2026-78438 in the wild and no public exploit code.
Sources
Also known as GHSA-6p3q-4gcg-xv4v.