LISTENING IN: Privacy Researcher Finds Anthropic’s Claude Desktop App Installs Undisclosed Native Messaging Bridge DO YOU HEAR ME NOW? A detailed technical analysis published by privacy and security researcher Alexander Hanff has raised serious concerns about Anthropic’s Claude Desktop application for macOS. Hanff, whose work is frequently referenced by Chief Privacy Officers and cybersecurity professionals, discovered the issue while auditing Native Messaging helpers on his own MacBook. According to the blog post, installing the Claude Desktop app automatically deploys a Native Messaging manifest file named com.anthropic.claude_browser_extension.json into the support directories of multiple Chromium-based browsers. This occurs even for browsers the user has never installed or does not use! The manifest file references a local binary located inside the Claude.app bundle at /Applications/Claude.app/Contents/Helpers/chrome-native-host. This binary functions as a bridge that allows pre-authorized browser extensions to communicate directly with the Claude Desktop app outside the browser’s sandbox, operating at full user privilege level via standard input/output. Key technical findings include: •The bridge pre-authorizes three specific Chrome extension IDs. •It is designed to remain dormant until activated by one of those extensions. •The manifest files are automatically recreated every time the Claude Desktop app launches, making permanent removal difficult. •Installation activity is logged in ~/Library/Logs/Claude/main.log, with timestamps confirming the files were written regardless of whether the browsers were present or supported. Hanff notes that the silent installation without user disclosure or consent is the central issue. Privacy, Security, and Potential Legal Implications. Corporations should not only note this but assume this is taking place. The researcher characterizes the behavior as “pre-installed spyware capability” for several reasons: •No clear notification or opt-in is provided to users during installation. •The process modifies configuration files across multiple browser vendors and creates directories for non-existent browsers. •Once active, the bridge could potentially expose authenticated web sessions (e.g., banking, email, or health portals), read decrypted page content, or enable automation. •The generic naming and automatic re-creation obscure the mechanism, resembling “dark patterns.” Hanff further contends that the practice may violate Article 5(3) of the EU’s ePrivacy Directive, which requires explicit consent before storing or accessing information on a user’s device. In response, he has issued a formal Cease and Desist letter to Anthropic, demanding that the company update the app to require explicit user opt-in (for example, only after the corresponding Chrome extension is installed) within 72 hours, or face further legal action. This revelation highlights ongoing challenges in the AI industry as companies develop increasingly “agentic” tools that require deep system and browser access. While such technical bridges are sometimes necessary for advanced functionality, transparency, documentation, and user control are considered essential by privacy advocates. Anthropic as expected has not issued a public statement addressing the specific allegations. Users who have installed Claude Desktop on macOS are advised be sure they like this idea. I sure don’t. 
Alexander Hanff’s full technical analysis: thatprivacyguy.com/blog/anth…