Jelsoft vBulletin accepts uploads of Cascading Style Sheets (CSS) and processes them in a way that allows remote authenticated administrato…

Jelsoft vBulletin accepts uploads of Cascading Style Sheets (CSS) and processes them in a way that allows remote authenticated administrators to gain shell access by uploading a CSS file that contains PHP code, then selecting the file via the style chooser, which causes the PHP code to be executed. NOTE: the vendor was unable to reproduce this issue in 3.5.x. NOTE: this issue might be due to direct static code injection.