The response function in the JSONP endpoint in WebService/Server/JSONRPC.pm in jsonrpc.cgi in Bugzilla 3.x and 4.x before 4.0.14, 4.1.x and 4.2.x before 4.2.10, 4.3.x and 4.4.x before 4.4.5, and 4.5.x before 4.5.5 accepts certain long callback values and does not restrict the initial bytes of a JSONP response, which allows remote attackers to conduct cross-site request forgery (CSRF) attacks, and obtain sensitive information, via a crafted OBJECT element with SWF content consistent with the _bz_callback character set.