CVE-2026-17086: ShortPixel Image Optimizer <= 6.5.5 - Authenticated (Author+) PHP Object Injection via Nested JSON Post Content
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ShortPixel Image Optimizer – Optimize Images, Convert WebP & AVIF (WordPress plugin)to a version that resolves this vulnerability.Fixed in 6.5.5 - Compensating control
Verify and remove any additional WordPress plugins or themes that contain a POP chain, since the vulnerability has no impact unless another plugin/theme with a POP chain is installed on the site.
Event History
Frequently Asked Questions
Which sites are realistically exposed to meaningful impact?
Sites running ShortPixel Image Optimizer version 6.5.5 or earlier are affected by the object injection flaw. Meaningful impact additionally requires another installed plugin or theme to provide a usable PHP POP chain, because no known POP chain exists in the vulnerable ShortPixel software itself.
What access does an attacker need?
An attacker must be authenticated to the WordPress site with Author-level privileges or higher. No user interaction is required.
What could an attacker do if a compatible POP chain is installed?
The available impact depends on the POP chain in the additional plugin or theme. Possible outcomes include arbitrary file deletion, retrieval of sensitive data, or code execution.