Mozilla Firefox before 3.0.7, Thunderbird before 2.0.0.21, and SeaMonkey before 1.1.15 decode invisible characters when they are displayed in the location bar, which causes an incorrect address to be displayed and makes it easier for remote attackers to spoof URLs and conduct 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.