Researchers at Tenet Security showed how anyone with a public Sentry DSN can inject a fake error report that coding agents like Claude Code, Cursor, and Codex will treat as a fix instruction. The agent fetches the malicious payload via the Model Context Protocol and runs arbitrary commands on the developer’s machine, exposing environment secrets and credentials. Sentry won’t close the write endpoint, leaving the fix to agent runtimes to filter untrusted data.

• A public write-only Sentry DSN lets attackers inject fake error reports that coding agents (Claude Code, Cursor, Codex) blindly treat as trusted fix instructions, leading to arbitrary code execution on developer machines.
• Tenet's tests across 2,388 organizations (including 71 Tranco top-1M sites) got an 85% success rate with 100+ confirmed code executions, hitting even a developer at a $250B Fortune 100 firm.
• The attack is invisible to traditional defenses (firewalls, EDR, WAFs, IAM) since it never touches victim infrastructure or needs passwords, and prompt-level "ignore untrusted data" instructions failed to stop it.
• Sentry isn't closing the vulnerable write endpoint, so the only real fix is runtime-level gating in the agent itself to sandbox or reject commands sourced from external/unauthenticated data.