A critical flaw (CVE-2026-82533, CVSS 9.4) in DeepSeek Harness, an open-source tool for running AI coding agents locally, let a sandboxed agent turn off its own sandbox with a single call to the tool’s own local web interface, switching its session into an unrestricted mode that skipped approval prompts. The bug stemmed from a function that trusted a spoofable ‘Host’ header instead of verifying the actual connection origin, so an agent tricked by attacker-supplied text it had read could escape confinement and run commands on the host without user approval. DeepSeek patched the issue in version 0.1.2-alpha.1 within days of disclosure.