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 became especially severe in the v85.x branch, where tokens were appended as the &auth= query parameter during network redirects to the operator’s proxy servers, exposing them in clear text within proxy logs. Earlier versions had already transmitted tokens via POST requests to a set-token endpoint and maintained backup endpoints on deno.dev and deno.net. A fix is available in Firefox starting with version 85.8.7, which stops token exfiltration by changing the playlist retrieval method, while a corresponding 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 a password or second factor, allowing actions ranging from reading and sending whispers to writing in chat and altering linked account settings.

The tokens function as bearer credentials: whoever possesses them can operate as the authenticated user. The most critical behavior appeared in the v85.x branch, where the extension added the token as the &auth= query parameter during network-level redirects to the operator’s proxy infrastructure. Because the token traveled inside a URL, it could remain in clear text inside proxy logs, greatly increasing exposure if those logs were accessed or leaked.

The forwarding occurred for nearly every channel a user opened, with the exception of a default list of ten channels. Starting with version 85.8.4, the extension also introduced a Channels with restrictions parameter that gave the 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 hosted on deno.dev and deno.net.

The correction is available in Firefox from version 85.8.7, which eliminates token transmission by altering the playlist retrieval method. The developer stated that an equivalent patch for Chrome is being prepared. Updating or disabling the extension stops further leakage, yet it does not invalidate tokens that have already been sent.

Recommended actions include immediately uninstalling or disabling Twitch Enhanced Viewer | JeetBot, revoking all active Twitch sessions from account settings, forcing re-authentication, and reviewing recent activity, private messages, and chat actions for unauthorized use. In managed environments, organizations should inventory installed extensions, block the affected identifiers pnhhdhhcadcjfckjhpmjneldiegbojfb in Chrome and twitchenhancedviewer@example.com in Firefox, and enforce allow-list policies for corporate browsers.

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