Firefox zero-day attack. Discontinue use of Firefox until resolved. - Compudent Systems
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Firefox zero-day attack. Discontinue use of Firefox until resolved.

Firefox zero-day attack. Discontinue use of Firefox until resolved.

Today, Wordfence is publishing an emergency bulletin to their customers and to the larger web community. A few hours ago a zero day vulnerability emerged in the Tor browser bundle and the Firefox web browser. We therefore suggest that you temporarily discontinue use of the Firefox browser, and switch to Chrome until the problem is resolved. This problem currently impacts Windows systems running Firefox versions 41 to 50, along with the current Tor Browser Bundle.

Wordfence reports that the vulnerability allows an attacker to execute code on your Windows workstation. The exploit is in the wild, meaning it’s now public and every hacker on the planet has access to it. There is no fix at the time of this writing.

Currently, this exploit causes a workstation report back to an IP address based at OVH in France. But this code can likely be repurposed to infect workstations with malware or ransomware. The exploit code is now public knowledge so we expect new variants of this attack to emerge rapidly.

This is a watering hole attack, meaning that a victim has to visit a website that contains this exploit code to be attacked. So our forensic team is keeping an eye on compromised WordPress websites and we expect to see this code show up on a few of them during the next few days. An attackers goal would be to compromise workstations of visitors to WordPress websites that have been hacked.

Wordfence Reporting: How this unfolded

On Tuesday just after noon Pacific time, someone published a 0 day exploit for Firefox and Tor to the tor browser mailing list.

Since then researcher Dan Guido posted a series of tweets with some analysis of the exploit itself.

Twitter user @TheWack0lian noticed the shellcode (code that executes on your Windows workstation once exploited) is very similar to shellcode likely used by the FBI back in 2013 to deanonymize visitors to child porn websites hosted by FreedomHosting. The FBI confirmed that they compromised that server and days later it was serving malware that would infect site visitor workstations. The code then reported site visitor real IP addresses, MAC addresses (network card hardware address) and windows computer name to a central server. This code is very similar.

What we found

The shell code in this attack calls back to IP address 5.39.27.226, which was a web server hosted at OVH in France. The site is now down. Our own research shows that if you look up this IP address in Shodan, it had an SSL certificate that is a wildcard for the energycdn.com domain name. That site for energycdn is simplistic and according to archive.org, it has not changed since 2014.

Googling energycdn.com shows that the domain is used frequently to host pirated content. Norton Safe Web reports it hosts viruses. Google Safe Browsing transparency report says the domain hosts malware and redirects to malicious sites.

One could speculate that the server at 5.39.27.226 was used by energycdn.com as one of their servers to host pirated content. Perhaps the server was compromised by whoever controls energycdn to host that content and then was reinfected by the perpetrator of this new malware variant. But we’re speculating.

Additional press coverage

Source: Emergency Bulletin: Firefox 0 day in the wild. What to do. – Wordfence



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