ShortPixel Image Optimizer <= 6.5.5 - Authenticated (Author+) PHP Object Injection via Nested JSON Post Content

Summary

The ShortPixel Image Optimizer – Optimize Images, Convert WebP & AVIF plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 6.5.5 via deserialization of untrusted input . This makes it possible for authenticated attackers, with author-level access and above, to inject a PHP Object. No known POP chain is present in the vulnerable software, which means this vulnerability has no impact unless another plugin or theme containing a POP chain is installed on the site. If a POP chain is present via an additional plugin or theme installed on the target system, it may allow the attacker to perform actions like delete arbitrary files, retrieve sensitive data, or execute code depending on the POP chain present.

Timeline

1. Sep 18, 2026, 3:38 AM UTCCVE published
2. Sep 18, 2026, 2:18 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Sep 18, 2026, 2:31 PM UTCRecord last updated

Affected versions

• shortpixel ShortPixel Image Optimizer – Optimize Images, Convert WebP & AVIF

  through 6.5.5

References 14