AgentsAugust 18, 2026via Ars Technica
Microsoft Copilot reveals secret input that allowed it to be hacked
Why it matters
Agent security is now a practitioner concern: this vulnerability class (parameter injection leading to credential exfiltration) is a real category of agent exploit that teams deploying autonomous systems need to understand and defend against.
Key signals
- Microsoft Copilot vulnerability: hidden parameter exploitable via link injection
- Attack vector: password theft when target clicks link
- Implication: agent input handling and sandboxing gaps are a deployment risk
- August 2026 disclosure
- Ars Technica source (credible security publication)
The hook
A hidden parameter in Microsoft Copilot enabled password theft via link clicks — exposing a critical vulnerability in how agentic systems handle user input.
Secret parameter allowed hackers to steal passwords when a target clicked on a link.