Mozilla Firefox is prone to a remote code-execution vulnerability. Successful exploits may allow an attacker to execute arbitrary code in the context of the user running the affected application. Failed attempts will likely result in denial-of-service conditions. The issue affects Firefox 3.5; other versions may also be vulnerable. NOTE: Remote code execution was confirmed in Firefox 3.5 running on Microsoft Windows XP SP2. A crash was observed in Firefox 3.5 on Windows XP SP3. UPDATE (July 15, 2009): Remote code execution is also possible in Firefox 3.5 running on Apple Mac OS X.
Block external access at the network boundary, unless external parties require service.
If global access isn't needed, filter access to the affected computer at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of successful exploits.
Run all software as a nonprivileged user with minimal access rights.
To reduce the impact of latent vulnerabilities, run all applications with the minimal amount of privileges required for functionality.
Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity. This includes but is not limited to requests that include NOP sleds and unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from successful exploits.
Do not follow links provided by unknown or untrusted sources.
To reduce the likelihood of successful exploits, never visit sites of questionable integrity or follow links provided by unfamiliar or untrusted sources.
Set web browser security to disable the execution of script code or active content.
Vendor advisories and fixes are available. Please see the references for details.