CVE-2026-15421 Speed Optimizer <= 7.8.0 - Authenticated (Contributor+) Stored Cross-Site Scripting via Image Tag Attributes
Authenticated contributors can inject arbitrary scripts via image tags in Speed Optimizer plugin when Lazy Load Media is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-15421?
CVE-2026-15421 is a medium-severity cross-site scripting vulnerability in siteground Speed Optimizer – The All-In-One Performance-Boosting Plugin, published on 19 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
The Speed Optimizer – The All-In-One Performance-Boosting Plugin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Image Tag Attributes in all versions up to, and including, 7.8.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is only exploitable when the site administrator has enabled the Lazy Load Media option in the plugin settings.
Weakness: CWE-79
Which versions are affected by CVE-2026-15421?
How do I fix CVE-2026-15421?
No fix has been published for CVE-2026-15421 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-2026-15421 being exploited?
There is no known exploitation of CVE-2026-15421 in the wild and no public exploit code.
Sources
Also known as GHSA-8r64-rxjj-mp32.