Adobe Acrobat Chrome Extension Flaw Enabled Silent Theft of WhatsApp Web Conversations
A critical vulnerability in the Adobe Acrobat extension for Chrome allowed attackers to silently extract private conversations, contacts, and account information from WhatsApp Web with just one click on a malicious webpage.
The flaw impacted roughly 329 million browser installations and did not require compromising WhatsApp, stealing credentials, or installing malware. Victims only needed to visit an apparently harmless page; the rest occurred automatically in the background.
Researchers at Guardio discovered the attack, which they named HermeticReader. It exploited an error in the extension’s internal messaging system that failed to verify the origin of incoming commands.
A hidden iframe loaded by the attacker site forced the extension to write data into its local storage and activate the built-in but normally disabled Hermes integration feature. This feature then served as an unauthorized bridge to WhatsApp Web, allowing the attacker to read chats, contacts, and account details in plaintext.
Throughout the attack the user continued viewing a normal webpage and received no warnings or prompts from the browser or the Adobe Acrobat extension.
Guardio responsibly disclosed the issue to Adobe. The company resolved the vulnerability in June and assigned it the identifier CVE-2026-48294. Adobe classified the bug as a UXSS vulnerability capable of causing cross-site data leakage between unrelated origins.
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