Threats Tagged 'browser extension'

Brazilian banking malware operation REF9334 has been deploying KREMLIN toolkit since May 2025, targeting Brazilian financial institutions through malicious browser extensions. The operation uses multi-stage JavaScript loaders, custom C++ installers, and exploits Chromium integrity mechanisms by manipulating Secure Preferences and regenerating required HMACs. Infrastructure leverages Ethereum smart contracts as dead-drop resolvers for dynamic C2 configuration. Seven distinct campaigns over 15 months show evolution from PULSAR RAT to REMCOS RAT delivery. Attackers impersonate twelve Brazilian banks through Portuguese-language lures, with transaction patterns clustering during São Paulo working hours. The malicious extensions intercept credentials, session tokens, and sensitive banking data through keylogging and request interception capabilities. Over 1,500 infections have been temporarily disrupted through network canary registration, with 98.75% of victims located in Brazil.

MediumMalwareBrazil#kremlin#browser extension#ethereum dead-drop

A malicious browser extension called 'Twitch Enhanced Viewer | JeetBot' distributed on Chrome Web Store and Firefox Add-ons captures and forwards users' live Twitch OAuth session tokens to Russian-controlled proxy servers. The extension, with approximately 30,000 Chrome users and 552 Firefox users, markets itself as a quality-of-life tool for blocking ads and unlocking streams. While delivering these features, it secretly extracts users' account-scoped OAuth tokens and forwards them as query parameters to operator-controlled infrastructure. Current versions append tokens inline during video playlist redirects, while earlier builds explicitly POSTed tokens to dedicated collection endpoints. The operator is identified as a commercial Russian bot service called JeetBot, with infrastructure hosted across German and cloud providers.

Type confusion in V8 in Google Chrome prior to 152.0.7977.82 allowed a remote attacker to execute arbitrary code inside the sandbox via a crafted HTML page. (Chromium security severity: High)

HighVulnerabilityUnited States#cve#cve-2026-85046#gemstone

Arctic Wolf Labs has been tracking multiple campaigns built around CastleLoader, a multi-stage shellcode loader that has evolved significantly. Three distinct campaigns were identified: Urutyka, Garrigin, and Noidret. The most significant development is the integration of NeedleStealer framework payloads, marking the first observed use of Rust and Golang tooling in this campaign cluster. NeedleStealer includes a Rust-based desktop cryptocurrency wallet spoofer targeting Ledger, Trezor, and Exodus wallets, and a Golang-based malicious browser extension installer. The campaigns utilize obfuscated PowerShell stagers, IronPython runtimes, and NodeJS-based shellcode injectors. Infrastructure analysis revealed consistent naming patterns, staged domains for future operations, and the use of fraudulently obtained code-signing certificates. The campaigns consistently deploy NetSupport RAT and CastleStealer alongside the new NeedleStealer payloads, suggesting an expansion toward high-value cryptocurrency targeting.

HighVulnerabilityUnited StatesCanada#cve#cve-2026-0257#cwe-565

A vulnerability in the web interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to log in to an affected device using a low-privileged account to access sensitive data within the impacted systems. This vulnerability is due to the presence of static user credentials for a low-privileged account. An attacker could exploit this vulnerability by using the account to log in to an affected system. A successful exploit could allow the attacker to log in to the affected system and access sensitive data as the low-privileged user.  Note: If the FMC management interface does not have public internet access, the attack surface that is associated with this vulnerability is reduced.   Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates. The reason is that this vulnerability can be used with other Cisco Secure FMC Software vulnerabilities to elevate privileges.

In January 2026, researchers identified a sophisticated malware framework dubbed OkoBot that targets cryptocurrency users through a multi-stage infection chain. The campaign begins with TookPS PowerShell scripts delivered via ClickFix attacks or fake software on GitHub. An automated SSH bot deploys over 20 malicious modules including HDUtil launcher, browser extension injectors installing Rilide stealer, and specialized tools like SeedHunter for wallet seed phrase theft and OkoSpyware for window capture. The framework uses VMProtect obfuscation, UAC bypass techniques, and maintains persistence through RDP access and scheduled tasks. Victims span more than 25 countries with concentrations in Brazil, Vietnam, Canada, Mexico, and Turkey. Attribution suggests Russian-speaking threat actors based on geoblocking patterns and Russian language artifacts.

MediumMalwareBrazilCanadaMexico+2#ssh tunnel#tevirat#tookps

ModHeader, a popular Chrome developer extension with over 800,000 users, was flagged and removed by Google for containing hidden spyware. Version 7.0.18 included a covert SDK disguised as a date library (dayjs) that harvested visited domain names, encrypted them using AES-GCM, and was configured to upload the data daily to api.stanfordstudies.com. Although the collection remained dormant due to an empty allowlist, the complete exfiltration infrastructure was present and operational. Additionally, the extension displayed active adware behavior, opening affiliate tabs on every update including on enterprise-managed machines. The malicious code shipped with official Chrome Web Store signatures, affecting both Chrome and Edge users. Forensic analysis revealed the extension locally stored 178MB of sensitive HTTP headers from all browsing activity, though no data was successfully exfiltrated from analyzed systems.

Malicious browser extensions distributed through Chrome Web Store and Firefox Add-ons marketplaces posed as free VPN services while secretly stealing clipboard data. The Chrome extension, with 146 users, and Firefox extension, with 3,499 users, initially functioned as proxy tools but later incorporated clipboard theft through staged updates. Chrome versions 1.1 onwards and Firefox version 1.3.3 onwards continuously monitored clipboard contents every 500-1500 milliseconds, capturing passwords, API keys, cryptocurrency addresses, and authentication tokens. Stolen data was chunked, tagged with session identifiers, and exfiltrated via HTTP to attacker-controlled infrastructure at multiple IP addresses. Both extensions shared code patterns, infrastructure, and exfiltration endpoints despite appearing as separate products, indicating coordinated malicious operations behind legitimate-appearing privacy tools.

Microsoft Threat Intelligence identified a malicious Chromium extension spoofing Perplexity AI to deceive users into installation. The extension's primary objective involves search traffic interception and data collection through Manifest Version 3 capabilities and declarativeNetRequest rules. It routes both full search queries and real-time keystrokes through attacker-controlled infrastructure hosted on a typosquatted domain before redirecting to legitimate search providers. The extension overrides browser default search settings, captures user input at keystroke-level, and uses suspicious permissions inconsistent with legitimate AI assistants. The threat demonstrates how actors operationalize AI branding as social engineering vectors. Google removed the extension following responsible disclosure. Organizations should strengthen user awareness training and implement layered security strategies to detect similar threats.

An initial access broker linked to Payouts King ransomware is deploying Edgecution, a sophisticated malware utilizing a malicious Microsoft Edge browser extension. The attack begins through social engineering via Microsoft Teams, impersonating IT staff and directing victims to fake Microsoft websites offering supposed Outlook updates. Edgecution comprises two components: a browser extension that communicates with command-and-control servers via websockets, and a Python-based backdoor. The extension abuses Chrome native messaging protocol to escape browser sandbox restrictions, enabling direct host access. This allows attackers to manipulate the filesystem, launch processes, and execute arbitrary code. The malware operates in a headless browser, remaining invisible to users. Deployment methods include AutoHotKey scripts, Windows batch scripts, and PowerShell scripts. The Python backdoor supports various commands including system information collection, filesystem access, and arbitrary code execution.