Malicious Browser Extensions Used for Enterprise Backdoors and Session Hijacking
Security researchers reported multiple malicious browser-extension campaigns abusing official extension stores and search-driven lures to compromise enterprise users. Huntress documented a Chrome Web Store extension, “NexShield – Advanced Web Guardian” (a near-clone of uBlock Origin Lite), distributed via search/advertising redirection and designed to intentionally “freeze” the browser and present a fake CrashFix security prompt that instructs users to paste and run commands via Win + R; this social-engineering step results in installation of a previously undocumented Windows RAT dubbed ModeloRAT on domain-joined endpoints. Reporting also tied the delivery to a traffic distribution system (KongTuke, also tracked as 404 TDS/TAG-124 and other aliases) used to profile victims and route them to payload delivery infrastructure that has been leveraged by other criminal operations, including ransomware affiliates.
Separately, Socket.dev analysis described five coordinated Chrome extensions targeting enterprise SaaS platforms (Workday, NetSuite, SuccessFactors) to enable account takeover via session hijacking, including continuous token theft and bidirectional cookie injection that can bypass MFA by replaying stolen session cookies. In parallel, Malwarebytes reported “sleeper” extension campaigns attributed to DarkSpectre (including GhostPoster and ShadyPanda) that turned previously benign extensions malicious after updates and used steganography (JavaScript hidden in extension images) to evade detection across Edge, Chrome, and Firefox, with large download counts and long dwell time. A separate Nextron Systems report described a related distribution pattern—malicious “free converter” apps promoted via malicious Google ads and made to look legitimate with code-signing certificates—highlighting the broader trend of search/advertising-driven initial access leading to persistent RAT deployment, though it is not the same extension-specific incident as the NexShield/CrashFix chain.
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