Bugzilla before 3.2.10, 3.4.x before 3.4.10, 3.6.x before 3.6.4, and 4.0.x before 4.0rc2 does not properly handle whitespace preceding a (1) javascript: or (2) data: URI, which allows remote attackers to conduct cross-site scripting (XSS) attacks via the URL (aka bug_file_loc) field.