Max-Severity React2Shell Vulnerability

Although Akira was once again the most active ransomware group in January, the threat landscape was more evenly distributed than it was throughout most of 2025. In December 2025, the three most active threat groups accounted for 57% of all ransomware and extortion activity; in January, the top three accounted for just 34%. Akira’s dominance also decreased to levels more consistent with early 2025, as the group was responsible for almost a third of all attacks in December but just 17% in January. 

The number of unique ransomware and extortion groups observed in January increased slightly, to 17, up from 14 in December. It is too early to assess whether this trend will be the new normal for 2026. It is also worth noting that overall activity in January was lower than in previous months, consistent with what Arete typically observes at the beginning of a new year.

Figure 1. Activity from all threat groups in January 2026

Throughout the month of January, analysts at Arete identified several distinct trends behind the threat actors perpetrating cybercrime activities: 

• In January, Arete observed the reemergence of the LockBit Ransomware-as-a-Service (RaaS) group, which deployed an updated “LockBit 5.0” variant of its ransomware. LockBit first announced the 5.0 version on the RAMP dark web forum in early September 2025, coinciding with the group’s six-year anniversary. The latest LockBit 5.0 variant has both Windows and Linux versions, with notable improvements, including anti-analysis features and unique 16-character extensions added to each encrypted file. However, it remains to be seen whether LockBit will return to consistent activity levels in 2026.

• The ClickFix social engineering technique, which leverages fake error dialog boxes to deceive users into manually executing malicious PowerShell commands, continued to evolve in unique ways in January. One campaign reported in January involved fake Blue Screen of Death (BSOD) messages manipulating users into pasting attacker-controlled code. During the month, researchers also documented a separate campaign, dubbed “CrashFix,” that uses a malicious Chrome browser extension-based attack vector. It crashes the web browser, displays a message stating the browser had "stopped abnormally," and then prompts the victim to click a button that executes malicious commands.

• Also in January, Fortinet confirmed that a new critical authentication vulnerability affecting its FortiGate devices is being actively exploited. The vulnerability, tracked as CVE-2026-24858, allows attackers with a FortiCloud account to log in to devices registered to other account owners due to an authentication bypass flaw in devices using FortiCloud single sign-on (SSO). This recent activity follows the exploitation of two other Fortinet SSO authentication flaws, CVE-2025-59718 and CVE-2025-59719, which were disclosed in December 2025.

Source

Arete Internal

Fortinet recently confirmed that its FortiGate devices are affected by a new critical authentication vulnerability that is being actively exploited. The vulnerability, tracked as CVE-2026-24858, allows attackers with a FortiCloud account to log in to devices registered to other account owners due to an authentication bypass flaw in devices using FortiCloud single sign-on (SSO). CISA added the vulnerability to its Known Exploited Vulnerabilities catalogue and gave federal agencies just three days to patch, which requires users to upgrade all devices running FortiOS, FortiManager, FortiAnalyzer, FortiProxy, and FortiWeb to fixed versions. This recent activity follows the exploitation of two other SSO authentication flaws, CVE-2025-59718 and CVE-2025-59719, which were disclosed last month.

What’s Notable and Unique

• There are strong indications that much of the recent exploitation activity was automated, with attackers moving from initial access to account creation within seconds.

• As observed in December 2025, the attackers’ primary target appears to be firewall configuration files, which contain a trove of information that can be leveraged in future operations.

• The threat actors in this campaign favor innocuous, IT-themed email and account names, with malicious login activity originating from cloud-init@mail[.]io and cloud-noc@mail[.]io, while account names such as ‘secadmin’, ‘itadmin’, ‘audit’, and others are created for persistence and subsequent activity.

Analyst Comments

This is an active campaign, and the investigation into these attacks is ongoing. Organizations relying on FortiGate devices should remain extremely vigilant, even after following patching guidance. With threat actors circumventing authentication, it’s crucial to monitor for and alert on anomalous behavior within your environment, such as the unauthorized creation of admin accounts, the creation or modification of access policies, logins outside normal working hours, and anything that deviates from your security baseline.

Sources

• Administrative FortiCloud SSO authentication bypass

• Multiple Fortinet Products’ FortiCloud SSO Login Authentication Bypass

• Arctic Wolf Observes Malicious Configuration Changes On Fortinet FortiGate Devices via SSO Accounts

• Arctic Wolf Observes Malicious SSO Logins on FortiGate Devices Following Disclosure of CVE-2025-59718 and CVE-2025-59719

Cyber Campfire delivers data-driven insights from Arete’s Threat Intelligence Team. In this episode, we discuss cyber threat trends, statistics, and emerging threat actors from December 2025. Tune in for an in-depth look at the evolving threat landscape and actionable insights for global organizations and security partners.

Recent research reveals two distinct but similar malicious Chrome browser extension campaigns that demonstrate how threat actors are increasingly abusing trusted browser extension ecosystems to gain initial access, steal sessions, and compromise enterprise environments.

What’s Notable and Unique

• In mid-January 2026, cybersecurity researchers uncovered a coordinated cluster of five malicious Chrome extensions masquerading as enterprise productivity or access management tools for popular Human Resource and Enterprise Resource Planning platforms such as Workday, NetSuite, and SAP SuccessFactors.

• Although published under different names, the extensions shared identical infrastructure, code patterns, and attack logic, indicating a single, well-organized operation. These extensions enabled session hijacking and full account takeover by abusing browser-level access.

• In January, researchers also documented a separate campaign, dubbed “CrashFix,” which uses a different but equally effective browser extension-based attack vector. In this case, a malicious Chrome extension named NexShield impersonated the legitimate uBlock Origin Lite ad blocker and was distributed through malicious ads that redirected users to the official Chrome Web Store where they would be prompted to download the malicious version.

• The technique mentioned above is yet another evolution of the ClickFix style social engineering that emerged in 2025, in which users are tricked into executing malicious commands themselves. In CrashFix attacks, following the instructions led to the execution of PowerShell commands that downloaded and installed ModeloRAT, a previously undocumented Python based remote access trojan.

Analyst Comments

Browser extensions are being weaponized as highly trusted initial access vectors, with attackers blending technical abuse (cookie theft, resource exhaustion) with social engineering (productivity branding, fake repair prompts). Together, these two recent findings demonstrate that malicious Chrome extensions pose a risk as a primary entry point for enterprise compromise, making browser extension governance, monitoring, and user education a critical defensive priority. Organizations should monitor for hidden PowerShell processes that are accessing browser cache folders and limit the use of PowerShell to privileged administrators. Organizations should also continue to promote and update their security awareness training, educating employees on newer social engineering techniques such as ClickFix.

Sources

• 5 Malicious Chrome Extensions Enable Session Hijacking in Enterprise HR and ERP Systems

• Dissecting CrashFix: KongTuke’s New Toy