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Browser Extension Security

Malicious and repurposed browser add-ons, marketplace review limits, and update-time trust in extension ecosystems.

Current stories

securityOne report1 publisher

Superior crew slips wallet-drainers into browser extensions on the version bump

Socket found 19 Chrome and Edge extensions carrying crypto-draining code, five of them bought from their original owners. The malware landed in updates after each listing had earned real installs, which is exactly what a one-time vetting pass never re-checks.

Reality

Evidence60
Adoption35
Hype gap+10
Incentives
Not scored
Confidence60
securityConfirmed3 publishers

Twitch extension in both browser stores forwards 30,604 users' live OAuth tokens to operator proxies

Socket found that Twitch Enhanced Viewer | JeetBot attaches viewers' live OAuth tokens to playlist requests routed through its operator's proxies, exempting ten Russian-language channels. The Firefox fix has shipped and the Chrome build is in review.

Perspective Coverage

4 publishers
Builder
Builder 26%
Operator
Operator 66%
Investor
Investor 8%

Reality

Evidence78
Adoption30
Hype gap+15
Incentives40
Confidence72
securityConfirmed3 publishers

Weizman's BragJack hijacks five Chromium AI assistants from a single installed extension

Gal Weizman showed that one malicious extension can take over the AI agents in Chrome, Comet, Edge, Neon and Claude in Chrome, with bounties from all five vendors to show for it. Installation is the only precondition.

Publishers:bleepingcomputer.com forever.security thehackernews.com

Perspective Coverage

3 publishers
Builder
Builder 54%
Operator
Operator 38%
Investor
Investor 8%

Reality

Evidence68
Adoption
Not scored
Hype gap+30
Incentives62
Confidence64
buildOne report1 publisher

A Firefox extension arms itself five seconds after install from a lookalike Google domain

The add-on shipped to Mozilla's store as a dispatcher and took its instructions afterwards from a page it opened itself, on a domain built to resemble googleusercontent.com.

Publishers:socket.dev

Reality

Evidence62
Adoption10
Hype gap−10
Incentives55
Confidence58
buildOne report1 publisher

KREMLIN forges Chromium's Secure Preferences HMACs with keys already on the endpoint

Elastic Security Labs describes a Brazilian banking operation that edits a Chrome or Edge profile and then signs its own edit using the OSCrypt and App-Bound keys sitting on the same machine. The browser loads the extension as approved.

Publishers:dev.to

Reality

Evidence62
Adoption35
Hype gap−10
Incentives45
Confidence58
securityOne report1 publisher

KREMLIN forges the HMACs Chromium uses to prove a user approved an extension

Elastic Security Labs tied 1,515 infections, almost all in Brazil, to a loader that waits for Chrome to close and then writes its own extension into the profile directory with integrity hashes the browser accepts.

Reality

Evidence58
Adoption32
Hype gap+10
Incentives62
Confidence55
securityOne report1 publisher

One extension commanded the AI in five Chromium browsers by seizing the page each one trusts

Forever Security showed the same technique working against Gemini in Chrome, Comet, Edge, Opera Neon and the Claude extension. Google and Microsoft have shipped fixes; the other three findings rest on the researchers' own account.

Reality

Evidence57
Adoption30
Hype gap+18
Incentives68
Confidence62
securityOne report1 publisher

KREMLIN installers forge Chrome's Secure Preferences HMACs to register a stealer extension

Elastic Security Labs says the Brazilian crew it calls REF9334 has been running this since at least May 2025, writing its extension into Chromium's Secure Preferences and reading C2 addresses out of an Ethereum smart contract.

Reality

Evidence62
Adoption42
Hype gap+12
Incentives55
Confidence58
buildOne report1 publisher

An ad-blocking Twitch extension appends 30,000 users' account tokens to a proxy URL

Socket's threat researchers found that Twitch Enhanced Viewer sends each viewer's account-scoped OAuth token to a Russian bot vendor's proxies as a query parameter, on a redirect the extension's own code shows works without it.

Publishers:socket.dev

Reality

Evidence74
Adoption52
Hype gap+14
Incentives62
Confidence66
buildOne report1 publisher

Four crypto extensions read session tokens from inside the tabs where traders are already logged in

Socket traced six Chrome and Firefox listings to one publisher operation whose collector reaches for Firebase access tokens and Axiom bundle keys. Chrome pulled four in July 2026. The Firefox one is still up.

Publishers:socket.dev

Reality

Evidence72
Adoption34
Hype gap+14
Incentives60
Confidence63
productOne report1 publisher

Talos found ClickFix operators moving their skimmer into a Tampermonkey userscript

The lure is a fake leaked vulnerability report promising 38% higher payouts to anyone greedy enough to paste the code. The command channel is a public Google Sheet that Talos reported twice and that stayed up.

Publishers:siliconangle.com

Reality

Evidence64
Adoption68
Hype gap−8
Incentives62
Confidence60
securityOne report1 publisher

ClickFix crews shift paste target to Chrome address bar or Tampermonkey

Cisco Talos traces a crypto skimmer running since October 2025 that keeps persistence in a Tampermonkey userscript and pulls its code from a public Google Sheet. Talos says most organisations are not the target.

Reality

Evidence66
Adoption20
Hype gap−12
Incentives55
Confidence58
buildOne report1 publisher

An MV3 extension pushes scoped cookies into a headless Lightpanda over a loopback CDP relay

The human still taps the security key, and what crosses to the agent is one origin's cookies, normalized and pushed over 127.0.0.1. The identity provider sits on the relay's blocklist, which is the part worth copying.

Publishers:dev.to

Reality

Evidence38
Adoption
Not scored
Hype gap+28
Incentives72
Confidence42
buildOne report1 publisher

Google's CDN delivered version 1.7.3.0 of an extension it had pulled six months earlier

Netskope Threat Labs puts the update between 20 and 31 July, and describes a Chrome sidebar that still earned an affiliate commission as users removed it. That says more about the update channel than about the install.

Publishers:dev.to

Reality

Evidence44
Adoption52
Hype gap+12
Incentives55
Confidence46
securityOne report1 publisher

N-able Passportal leaked whole vaults to any page: v3.49.6 stops the leak, not the tokens

A missing origin check let any site pull an MSP's decrypted vault and keep access for up to 100 days, according to the researchers who found it. Installing the patch does not retire tokens already taken.

Publishers:amibeingpwned.com

Reality

Evidence63
Adoption58
Hype gap+14
Incentives62
Confidence56
productOne report1 publisher

iOS 27 moves Safari extensions from a developer artifact to a text box in the page menu

Apple Intelligence groups Safari tabs into topics and builds extensions from typed prompts. Five of Apple's eight sample prompts change the page itself; the guide says nothing about review or sharing.

Publishers:macrumors.com

Reality

Evidence30
Adoption12
Hype gap+28
Incentives62
Confidence45
buildOne report1 publisher

Socket turns on continuous scanning for all 97,100 Firefox add-ons

Browser extensions update themselves silently unless new permissions are requested. Socket says it is now watching every version of every add-on in Mozilla's directory.

Publishers:socket.dev

Reality

Evidence44
Adoption17
Hype gap+26
Incentives82
Confidence48
buildOne report1 publisher

77 linked Firefox add-ons, one pipeline: store review is a checkpoint, not a control

Socket says 40 of the 77 extensions it tracked are confirmed credential and wallet stealers, and nine of them were repurposed from sports-score shells under the same add-on IDs.

Publishers:socket.dev

Reality

Evidence70
Adoption24
Hype gap+14
Incentives72
Confidence58