Yii is an open source PHP web framework. yiisoft/yii before version 1.1.29 are vulnerable to Remote Code Execution (RCE) if the application calls `unserialize()` on arbitrary user input. An attacker may leverage this vulnerability to compromise the host system. A fix has been developed for the 1.1.29 release. Users are advised to upgrade. There are no known workarounds for this vulnerability.
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.