Zenity Discloses Zero-Click Browser Attacks on ChatGPT Atlas and Claude Extension

August 6, 2026 at 05:54 PM2 min

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AI security company Zenity disclosed two zero-click browser attack techniques on Wednesday that exploit ChatGPT Atlas and Claude in Chrome, enabling account takeovers, phishing, and unauthorized purchases. The vulnerabilities stem from architectural design flaws in agentic browsers that break the Same-Origin Policy, allowing attackers to hijack user sessions through planted comments or emails.

ChatGPT Atlas Hijacking

Zenity found that ChatGPT Atlas is vulnerable to indirect prompt injection through intentional 'intent collision.' By planting a single comment on an X thread, attackers can redirect the agent to a malicious page, then navigate to WhatsApp Web to read the victim's entire contact list and send phishing messages to every contact. In a second scenario, Atlas adds items to an Amazon cart and updates the shipping address to the attacker's location, then instructs Amazon's built-in AI assistant Rufus to place the order because direct purchase clicks are blocked. OpenAI acknowledged the report in January 2026 but has not released a patch.

Claude Chrome Extension Compromise

The Claude Chrome extension can be compromised via a zero-click attack that uses malicious emails containing invisible prompt structures. When a user asks Claude to summarize recent emails, the extension interprets the hidden instructions as direct commands. Attackers bypass standard safety mechanisms by hosting custom NPM packages on a rogue CDN, escalating the indirect prompt injection into full account takeover across multiple web platforms.

Agentic Browser Architecture Flaw

Both attacks exploit a fundamental design issue in agentic browsers: they act as a single entity across multiple authenticated tabs, effectively breaking the Same-Origin Policy and resurrecting cross-site request forgery risks. This enables malicious instructions from an untrusted page to control the agent on any site where the user is logged in. Zenity described the vulnerabilities as intentional core capabilities rather than traditional software bugs, making them difficult to patch without altering essential functionality.