ExPatch

Telegram Desktop HTML Export Flaw Allowed Stealthy JavaScript Injection into Chat History

Researchers at ExPatch identified a vulnerability in Telegram Desktop that enabled attackers to embed malicious JavaScript into exported HTML chat histories without user detection. The flaw stemmed from insufficient sanitization of button captions added by bots, allowing hidden scripts to execute when the HTML file was opened in a browser. Malicious messages could be forwarded into chats and remain dormant until export, potentially exfiltrating messages, sender names, and timestamps to attacker servers. The issue affected versions 4.15.1 through 6.9.3, with fixes released in beta 6.9.4 and stable version 7.0.1 on July 14. No in-the-wild exploitation was observed, though the attack required specific conditions including an unpatched export and JavaScript-enabled browser. Users are advised to re-export chats after updating or open old files with JavaScript disabled.