Ambient Authority
A security failure mode where an agent can use tools, credentials, or host permissions simply because they are present in its runtime.
Plain English
The agent gets the keys because it is in the room, not because this specific task should have them.
Example
A browser agent running as the user can read email and send messages unless each action is separately scoped or approved.
Why it matters
Ambient authority turns prompt injection and tool mistakes into real side effects, especially in MCP and desktop-agent deployments.