Quick.CMS deserializes user-controlled data received over plaintext HTTP without ensuring integrity or authenticity. This allows attackers to tamper with serialized payloads in transit and inject malicious objects. Because deserialization is performed without proper validation or class restrictions, crafted payloads can trigger dangerous magic methods (e.g., __wakeup() and __destruct()) and leverage gadget chains, resulting in arbitrary code execution. Exploitation is triggered automatically when an administrator accesses the admin panel.
When successfully exploited, this vulnerability allows attackers to execute arbitrary code on the server via manipulated serialized data transmitted over an unprotected channel.
This issue was mitigated by limiting the communication to HTTPS in a patch for version 6.8 published on 14.05.2026, deployments without this patch remain vulnerable.