The history (revision control) function in TWiki 02-Sep-2004 and earlier allows remote attackers to execute arbitrary code via shell metacharacters, as demonstrated via the rev parameter to TWikiUsers.

TWiki 01-Dec-2000 up to 4.0.3 allows remote attackers to bypass the upload filter and execute arbitrary code via filenames with double extensions such as ".php.en", ".php.1", and other allowed extensions that are not .txt. NOTE: this is only a vulnerability when the server allows script execution in the pub directory.