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 4.0.0, 4.0.1, and 4.0.2 allows remote attackers to gain Twiki administrator privileges via a TWiki.TWikiRegistration form with a modified action attribute that references the Sandbox web instead of the user web, which can then be used to associate the user's login name with the WikiName of a member of the TWikiAdminGroup.

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 (1) rdiff and (2) preview scripts in TWiki 4.0 and 4.0.1 ignore access control settings, which allows remote attackers to read restricted areas and access restricted content in TWiki topics.