Interpretation conflict in YaBB before 2.1 allows remote authenticated users to inject arbitrary web script or HTML via HTML in a file with a GIF file extension, which causes the HTML to be executed by a victim who views the file in Internet Explorer as a result of CVE-2005-3312. NOTE: it could be argued that this vulnerability is due to a design flaw in Internet Explorer and the proper fix should be in that browser; if so, then this should not be treated as a vulnerability in YaBB.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23020
http://www.yabbforum.com/downloads.php