The core Upload module in Drupal 4.7.x before 4.7.8 and 5.x before 5.3 places the .html extension on a whitelist, which allows remote attackers to conduct cross-site scripting (XSS) attacks by uploading .html files.

The hook_comments API in Drupal 4.7.x before 4.7.8 and 5.x before 5.3 does not pass publication status, which might allow attackers to bypass access restrictions and trigger e-mail with unpublished comments from some modules, as demonstrated by (1) Organic groups and (2) Subscriptions.

Drupal 5.2 and earlier does not properly unset variables when the input data includes a numeric parameter with a value matching an alphanumeric parameter's hash value, which allows remote attackers to execute arbitrary PHP code by invoking the drupal_eval function through a callback parameter to the default URI, as demonstrated by the _menu[callbacks][1][callback] parameter. NOTE: it could be argued that this vulnerability is due to a bug in the unset PHP command (CVE-2006-3017) and the proper fix should be in PHP; if so, then this should not be treated as a vulnerability in Drupal.

Multiple cross-site scripting (XSS) vulnerabilities in Drupal 5.x before 5.2, and 4.7.x before 4.7.7, (1) allow remote attackers to inject arbitrary web script or HTML via "some server variables," including PHP_SELF; and (2) allow remote authenticated administrators to inject arbitrary web script or HTML via custom content type names.

The (1) Textimage 4.7.x before 4.7-1.2 and 5.x before 5.x-1.1 module for Drupal and the (2) Captcha 4.7.x before 4.7-1.2 and 5.x before 5.x-1.1 module for Drupal allow remote attackers to bypass the CAPTCHA test via an empty captcha element in $_SESSION.