Reflected Cross-site scripting (XSS) vulnerability in Yii Framework before 2.0.11, when development mode is used, allows remote attackers to inject arbitrary web script or HTML via crafted request data that is mishandled on the debug-mode exception screen.
https://github.com/yiisoft/yii2/pull/13401
https://github.com/yiisoft/yii2/commit/97171a0db7cda0a49931ee0c3b998ef50bd06756
http://www.yiiframework.com/news/123/yii-2-0-11-is-released/