Yii 2 before 2.0.52 mishandles the attaching of behavior that is defined by an __class array key, a CVE-2024-4990 regression, as exploited in the wild in February through April 2025.
https://www.securityweek.com/craft-cms-zero-day-exploited-to-compromise-hundreds-of-websites/
https://thehackernews.com/2025/04/hackers-exploit-critical-craft-cms.html
https://sensepost.com/blog/2025/investigating-an-in-the-wild-campaign-using-rce-in-craftcms/
https://www.yiiframework.com/news/709/please-upgrade-to-yii-2-0-52
https://github.com/yiisoft/yii2/pull/20232#issuecomment-2252459709
https://github.com/yiisoft/yii2/pull/20232
https://github.com/yiisoft/yii2/compare/2.0.51...2.0.52
https://github.com/yiisoft/yii2/commit/40fe496eda529fd1d933b56a1022ec32d3cd0b12