Blocksy <= 2.1.41 - Authenticated (Contributor+) PHP Object Injection via Deserialization of Untrusted Data via 'blocksy_meta' REST API Field

Summary

The Blocksy theme for WordPress is vulnerable to PHP Object Injection leading to Remote Code Execution via the 'blocksy_meta' REST API field and the V200 database migration in versions up to and including 2.1.35. This is due to insufficient input sanitization in the blocksy_sanitize_post_meta_options() function, which only blocks values containing '<' or '>' and does not prevent serialized PHP object strings from being stored in post meta, combined with the SearchReplacer::run_recursively() function unconditionally deserializing all string values via @unserialize() during migration without restricting allowed classes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject a serialized Blocksy\RaiiPattern object into post meta that, when the V200 migration runs on an upgraded site, is deserialized and triggers RaiiPattern::__destruct(), which executes arbitrary PHP callables via call_user_func().

Timeline

1. Jun 9, 2026, 8:29 AM UTCCVE published
2. Jun 9, 2026, 12:55 PM UTCCISA SSVC assessment

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

3. Jun 9, 2026, 12:56 PM UTCRecord last updated

Affected versions

• creativethemeshq Blocksy

  through 2.1.41

References 13