CVE-2026-5217 Optimole <= 4.2.2 - Unauthenticated Stored Cross-Site Scripting via Srcset Descriptor Parameter
Unauthenticated attackers can inject arbitrary scripts via the srcset descriptor parameter in the Optimole WordPress plugin, leading to stored XSS.
- 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-2026-5217?
CVE-2026-5217 is a high-severity cross-site scripting vulnerability in Optimole – Optimize Images in Real Time, published on 11 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The Optimole – Optimize Images | Convert WebP & AVIF | CDN & Lazy Load | Image Optimization plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 4.2.2. This is due to insufficient input sanitization and output escaping on the user-supplied 's' parameter (srcset descriptor) in the unauthenticated /wp-json/optimole/v1/optimizations REST endpoint. The endpoint validates requests using an HMAC signature and timestamp, but these values are exposed directly in the frontend HTML making them accessible to any visitor. The plugin uses sanitize_text_field() on the descriptor value of rest.php, which strips HTML tags but does not escape double quotes. The poisoned descriptor is then stored via transients (backed by the WordPress options table) and later retrieved and injected verbatim into the srcset attribute of tag_replacer.php without proper escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts into pages that will execute whenever a user accesses the injected page.
Weakness: CWE-79
Which versions are affected by CVE-2026-5217?
How do I fix CVE-2026-5217?
No fix has been published for CVE-2026-5217 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-2026-5217 being exploited?
There is no known exploitation of CVE-2026-5217 in the wild and no public exploit code.
Sources
Also known as GHSA-8g9h-q4wq-r7gp.