• Sonar’s Vulnerability Research Team recently discovered a critical Cross-Site Scripting (XSS) vulnerability in Roundcube, a popular open-source webmail software.
• When a victim views a malicious email in Roundcube sent by an attacker, the attacker can execute arbitrary JavaScript in the victim's browser.
• Attackers can abuse the vulnerability to steal emails, contacts, and the victim's email password as well as send emails from the victim's account.
• In October 2023, ESET Research reported that a similar vulnerability was actively used by the APT group Winter Vivern to attack European government entities.
• Roundcube administrators should update to the patched version 1.6.8 or 1.5.8 as soon as possible.
• All discovered issues are tracked as CVE-2024-42008, CVE-2024-42009, CVE-2024-42010.

The Winter Vivern Russian hacking group has been exploiting a Roundcube Webmail zero-day since at least October 11 to attack European government entities and think tanks.

ESET Research discover campaigns by the Winter Vivern APT group that exploit a zero-day XSS vulnerability in the Roundcube Webmail server and target governmental entities and a think tank in Europe.

Recorded Future's Insikt Group, in partnership with Ukraine's Computer Emergency Response Team (CERT-UA), has uncovered a campaign targeting high-profile entities in Ukraine that was cross-correlated with a spearphishing campaign uncovered by Recorded Future’s Network Traffic Intelligence. The campaign leveraged news about Russia’s war against Ukraine to encourage recipients to open emails, which immediately compromised vulnerable Roundcube servers (an open-source webmail software), using CVE-2020-35730, without engaging with the attachment. We found that the campaign overlaps with historic BlueDelta activity exploiting the Microsoft Outlook zero-day vulnerability CVE-2023-23397 in 2022.