Misbehavior1 sourceFirst seen
Your coding agent reads the invisible ink. The file looked empty. The AI had other plans.
Ourtake
Invisible characters are the perfect hiding spot for instructions, and the AI sees them even when you don't.
What happened
A security researcher showed that Windsurf Cascade, a coding agent, follows instructions hidden in files using invisible Unicode Tag characters that the developer cannot see. In a demo using Claude Sonnet 3.7, a file that appeared empty caused the agent to invoke its web tool. The researcher disclosed the issue to Windsurf on May 30, 2025, and Windsurf later said it was working on fixes.