Flaw in Adobe Extension With 300M Installs Enabled WhatsApp Data Theft

Summary

A critical vulnerability in Adobe's Acrobat Chrome extension, installed on over 300 million browsers, allowed attackers to steal WhatsApp messages and contacts. The exploit, named HermeticReader, required victims to visit a malicious website, which then leveraged a flaw in the extension's messaging system to scrape data. Adobe patched the vulnerability, assigned CVE-2026-48294, in June.

Full text

A highly popular Chrome extension made by Adobe was affected by a vulnerability that could have been exploited to silently steal a user’s WhatsApp chats and contacts. According to web and browser security firm Guardio, whose researchers discovered and reported the vulnerability to Adobe, an attacker could have stolen users’ WhatsApp data simply by tricking them into visiting a seemingly harmless webpage. The exploit did not involve a WhatsApp vulnerability, malware deployment, compromised credentials, or access to the targeted device. The attack, dubbed HermeticReader, affected the Adobe Acrobat Chrome extension, which is installed in approximately 329 million browsers. Adobe patched the vulnerability in June, shortly after being informed of its existence. The software giant assigned it CVE-2026-48294 and described it as a UXSS-class cross-origin data disclosure vulnerability. Under the hood, the attack abuses a lack of security checks within the Adobe extension’s internal messaging system. When a victim loads the malicious site, a hidden frame tricks the extension into accepting unverified commands. Advertisement. Scroll to continue reading. This allows the attacker to silently write to the extension’s local storage and enable Hermes, a dormant integration engine built by Adobe. Once activated, this engine bridges the gap to WhatsApp Web, enabling the attacker to invisibly scrape the victim’s private chats, contacts, and account details in plain text. Guardio has published a video showing a HermeticReader attack in action: Related: Vibe-Coded Apps Riddled With Exploitable Security Flaws Related: Meta Paid $78,000 Bounty for Vulnerability Exposing Customer Support Data Related: OpenSSL Silently Fixes ‘HollowByte’ DoS Vulnerability Written By Eduard Kovacs Eduard Kovacs (@EduardKovacs) is senior managing editor at SecurityWeek. He worked as a high school IT teacher before starting a career in journalism in 2011. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. Daily Briefing Newsletter Subscribe to the SecurityWeek Email Briefing for the latest cybersecurity threats, trends, and expert insights. 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Indicators of Compromise

• cve — CVE-2026-48294

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