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.

TWiki 4.0, 4.0.1, and 20010901 through 20040904 allows remote authenticated users with edit rights to cause a denial of service (infinite recursion leading to CPU and memory consumption) via INCLUDE by URL statements that form a loop, such as a page that includes itself.

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.