Twitch Enhanced Viewer Extension Leaks OAuth Tokens From Nearly 31,000 Users

The browser extension Twitch Enhanced Viewer | JeetBot, available in the official Chrome Web Store and Mozilla Add-ons, secretly forwarded OAuth session tokens to proxies controlled by its operator. These bearer tokens allow full account takeover without passwords or second-factor authentication, enabling actions such as reading and sending whispers, posting in chat, and modifying account settings. The issue surfaced prominently in the v85.x branch where tokens were appended as the &auth= query parameter during network redirects to operator-controlled proxy servers, exposing them in clear text within proxy logs. Earlier v4.x versions had already transmitted tokens via POST requests to a set-token endpoint and backup servers on deno.dev and deno.net. A fix appeared in Firefox version 85.8.7 that stops token exfiltration by altering playlist retrieval, while a Chrome patch is in preparation. Users are advised to uninstall the extension immediately, revoke all active Twitch sessions, and review recent account activity for signs of unauthorized use.

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The browser extension Twitch Enhanced Viewer | JeetBot, distributed through the official Chrome Web Store and Mozilla Add-ons, forwarded OAuth session tokens to proxies under the control of its operator. With these tokens, an attacker can hijack accounts without needing the password or bypassing two-factor authentication, allowing actions ranging from reading and sending whispers to writing in chat and altering linked account settings.

The tokens function as bearer credentials: anyone in possession can impersonate the user on Twitch. The most critical behavior appeared in the v85.x branch, which added the token as the &auth= query parameter during network-level redirects to operator-controlled proxy servers. Because the token traveled inside URLs, it could remain in clear text inside proxy logs, greatly increasing exposure if those logs were accessed improperly or leaked.

The forwarding occurred for nearly every channel a user opened, with the sole exception of a hardcoded list of ten channels. Starting with version 85.8.4, the extension also exposed a Channels with restrictions setting that gave an appearance of control while the underlying exfiltration continued. Earlier v4.x releases had already sent tokens via POST to a set-token endpoint and maintained backup endpoints on deno.dev and deno.net.

Remediation and Recommendations

The corrected version for Firefox, 85.8.7, eliminates token transmission by changing the playlist retrieval method. An equivalent Chrome update is being prepared. Updating or disabling the extension stops further leakage but does not invalidate tokens already sent. Users should therefore uninstall or disable Twitch Enhanced Viewer | JeetBot immediately, close all active Twitch sessions from account settings, and re-authenticate to force session rotation. Reviewing recent activity, private messages, and chat actions is also recommended.

In managed environments the incident highlights the classic supply-chain risk posed by extensions that can intercept or redirect traffic for authenticated services. Basic hygiene includes maintaining an inventory of installed extensions, blocking the affected identifiers pnhhdhhcadcjfckjhpmjneldiegbojfb in Chrome and twitchenhancedviewer@example.com in Firefox, and enforcing allow-lists on corporate browsers.

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