Claude Desktop Reportedly Adds Browser Access Bridge to Multiple Chromium-Based Browsers

### Executive Summary Privacy researcher Alexander Hanff discovered that Anthropic's Claude Desktop for macOS automatically drops a Native Messaging manifest (com.anthropic.claude_browser_extension.json) into the application support folders of up to seven Chromium-based browsers, pre-authorizing three Chrome extension IDs to invoke a helper binary. This silent, persistent installation occurs without user consent (even for browsers not installed) and rewrites manifests on launch, increasing attack surface and raising risks of out-of-sandbox execution and sensitive data exposure, though the report does not present evidence of active exploitation.