LayerX research found dozens of Chrome extensions, reaching millions of users, that legally sell or share user data under terms accepted at install. Among ad blockers, it confirmed eight reserving the right to sell or share user information, together reaching over 5.5 million users. Stands AdBlocker, with three million users, sells browsing data for market analytics, and Poper Blocker, with two million users, discloses selling identifiers, browsing activity, and behavioral profiles inferred from visited URLs. Smaller ad blockers route browsing data and even AI conversations through data brokers. The finding shows tools installed to stop tracking can themselves become data exfiltration channels, a browser extension supply chain risk static malware scanning misses.
Researchers at Forever Security showed that a single malicious browser extension can hijack the AI assistant built into several AI-enabled browsers, including Chrome, Edge, Comet, Opera Neon, and Claude in Chrome. The core problem is that putting an AI agent inside the browser reopens a privilege-escalation path browsers normally work to close, letting a low-privilege extension reach a high-privilege part of the browser. Two of the findings received identifiers, one in Chrome, patched in January, and one in Edge, patched in July, while the others were fixed through bug bounties without dates. There is no evidence of real-world use yet, and each method still requires the user to install the extension.
Researchers at Socket found that a browser extension called "Twitch Enhanced Viewer," installed by roughly 30,000 Chrome and Firefox users, secretly forwards users' live Twitch session tokens to proxy servers run by a Russian-language bot service. Those tokens let anyone holding them act on the account without the password or two-factor authentication. The extension's advertised features, like ad blocking, forced 1080p, and region unlocking, are real and serve as cover: to deliver them it routes Twitch's video requests through operator-controlled proxies and skims the authentication token along the way. Earlier versions posted stolen tokens to a dedicated collection endpoint. Affected users should remove it and sign out of all Twitch sessions.
Researchers disclosed a post-exploitation toolkit called PEEP that turns Chrome and Edge into backdoors for stealing credentials and running commands on the host. After an attacker already has administrative or code-execution access, PEEP's installer injects a malicious extension disguised as a bookmarks tool directly into browser profiles, forging Chromium's own integrity settings to bypass the Web Store and skip user approval prompts. The planted extension then serves as a covert channel to harvest credentials and execute operating-system commands. Because it abuses a trusted, ever-present browser and hides its extension from the usual checks, it can persist quietly on a compromised machine, a reminder that browsers themselves are a rich post-compromise attack surface.
Guardio Labs disclosed HermeticReader, a flaw chain in the Adobe Acrobat extension for Chrome that let an attacker controlled web page read data from a visitor's WhatsApp Web session. Tracked as CVE-2026-48294 and rated 7.4, it is a cross origin disclosure issue affecting versions up to 26.5.2.2, installed on roughly 329 million browsers. Any site could disguise commands as internal extension messages, activate the extension's WhatsApp integration, and redirect its privileged page operations into the WhatsApp tab, extracting chats, contacts, and message previews. No malware, stolen credentials, or WhatsApp flaw was involved. Adobe patched within days.
Google and Microsoft removed ModHeader, a header-editing browser extension popular with developers, with about 1.6 million installs, after researchers at Stripe OLT found a hidden browsing-history collector inside the official, signed store version. The collector was dormant, gated off by an empty allow-list, and no evidence has emerged that it ever sent data, but its presence in a trusted, signed extension is the concern. Its design frustrated automated review: the data was encrypted, the upload was switched off so sandboxes saw nothing leave, and malicious code was blended into a legitimate codebase, so scanners rated it low risk. It is a reminder that a store signature proves origin, not safe behavior.
Zscaler detailed Edgecution, a malicious Microsoft Edge extension used in ransomware-linked intrusions that abuses Chrome's native messaging feature, which normally lets extensions talk to desktop apps, to break out of the browser sandbox and run a Python backdoor on the host. The extension beacons to a command server and relays commands to the backdoor, giving attackers filesystem access and code execution, while running in a hidden headless browser to stay invisible. Attacks start with social engineering on Microsoft Teams, where the actor poses as IT support and directs employees to a fake "Outlook Updates" page. Researchers tie the activity to an access broker linked to the Payouts King ransomware operation.
TrustStrike Labs