The heart of the problem lies with the history.dat file that Firefox creates, according to a posting on Packet Storm. The exploit creates a very large entry which Firefox then saves into the history.dat file. This causes the browser to crash the next time it is opened, and each time after that until the history.dat file is deleted from the system.
The author of the exploit points out that average users may have difficulty figuring out this fix, preventing browser use and effectively creating a denial of service condition. In the past there have been debates over browser bugs and if they are truly denial of service attacks - todays bug is sure to rekindle these arguments.
The final line of the exploit description warns that code execution is a possibility with some modifications to the sample exploit.
Posted by: Peter Laborge