WebUpgrade in Netsweeper before 3.1.10, 4.0.x before 4.0.9, and 4.1.x before 4.1.2 allows remote attackers to bypass authentication and create a system backup tarball, restart the server, or stop the filters on the server via a ' (single quote) character in the login and password parameters to webupgrade/webupgrade.php.  NOTE: this was originally reported as an SQL injection vulnerability, but this may be inaccurate.