Operation ForumTroll: APT attack with Google Chrome zero-day exploit chain

[harlan4096]

In mid-March 2025, Kaspersky technologies detected a wave of infections by previously unknown and highly sophisticated malware. In all cases, infection occurred immediately after the victim clicked on a link in a phishing email, and the attackers’ website was opened using the Google Chrome web browser. No further action was required to become infected.

All malicious links were personalized and had a very short lifespan. However, Kaspersky’s exploit detection and protection technologies successfully identified the zero-day exploit that was used to escape Google Chrome’s sandbox. We quickly analyzed the exploit code, reverse-engineered its logic, and confirmed that it was based on a zero-day vulnerability affecting the latest version of Google Chrome. We then reported the vulnerability to the Google security team. Our detailed report enabled the developers to quickly address the issue, and on March 25, 2025, Google released an update fixing the vulnerability and thanked us for discovering this attack.


Acknowledgement for finding CVE-2025-2783 (excerpt from security fixes included into Chrome 134.0.6998.177/.178)

We have discovered and reported dozens of zero-day exploits actively used in attacks, but this particular exploit is certainly one of the most interesting we’ve encountered. The vulnerability CVE-2025-2783 really left us scratching our heads, as, without doing anything obviously malicious or forbidden, it allowed the attackers to bypass Google Chrome’s sandbox protection as if it didn’t even exist. The cause of this was a logical error at the intersection of Google Chrome’s sandbox and the Windows operating system. We plan to publish the technical details of this vulnerability once the majority of users have installed the updated version of the browser that fixes it. 

Our research is still ongoing, but judging by the functionality of the sophisticated malware used in the attack, it seems the attackers’ goal was espionage. The malicious emails contained invitations allegedly from the organizers of a scientific and expert forum, “Primakov Readings”, targeting media outlets and educational institutions in Russia. Based on the content of the emails, we dubbed the campaign Operation ForumTroll.


Example of a malicious email used in this campaign (translated from Russian)

At the time of writing, there’s no exploit active at the malicious link – it just redirects visitors to the official website of “Primakov Readings”. However, we strongly advise against clicking on any potentially malicious links.

The exploit we discovered was designed to run in conjunction with an additional exploit that enables remote code execution. Unfortunately, we were unable to obtain this second exploit, as in this particular case it would have required waiting for a new wave of attacks and exposing users to the risk of infection. Fortunately, patching the vulnerability used to escape the sandbox effectively blocks the entire attack chain.


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