Mozilla Firefox 3.x before 3.0.5 and 2.x before 2.0.0.19, Thunderbird 2.x before 2.0.0.19, and SeaMonkey 1.x before 1.1.14 does not properly parse URLs with leading whitespace or control characters, which might allow remote attackers to misrepresent URLs and simplify phishing attacks.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.