Bugzilla 2.19.3 through 2.20 does not properly handle "//" sequences in URLs when redirecting a user from the login form, which could cause it to generate a partial URL in a form action that causes the user's browser to send the form data to another domain.

SQL injection vulnerability in whineatnews.pl in Bugzilla 2.17 through 2.18.4 and 2.20 allows remote authenticated users with administrative privileges to execute arbitrary SQL commands via the whinedays parameter, as accessible from editparams.cgi.

Bugzilla 2.18rc1 through 2.18.3, 2.19 through 2.20rc2, and 2.21 allows remote attackers to obtain sensitive information such as the list of installed products via the config.cgi file, which is accessible even when the requirelogin parameter is set.

Bugzilla 2.19.1 through 2.20rc2 and 2.21, with user matching turned on in substring mode, allows attackers to list all users whose names match an arbitrary substring, even when the usevisibilitygroups parameter is set.

Bugzilla 2.17.x, 2.18 before 2.18.2, 2.19.x, and 2.20 before 2.20rc1 inserts a bug into the database before it is marked private, which introduces a race condition and allows attackers to access information about the bug via buglist.cgi before MySQL replication is complete.

The Flag::validate and Flag::modify functions in Bugzilla 2.17.1 to 2.18.1 and 2.19.1 to 2.19.3 do not verify that the flag ID is appropriate for the given bug or attachment ID, which allows users to change flags on arbitrary bugs and obtain a bug summary via process_bug.cgi.