Matt Robb wanted to sell his computer keyboard.

So he put it on Facebook Marketplace.

As a test, he let Meta's new AI agent Muse do the sale.

Within one day, a buyer Robb did not know came to his house late at night.

Muse made a deal by itself.

It shared Robb's home address after it agreed to a pickup.

It even sent a message from his account: "Yep, I'm here!"

Robb did not know about any of this.

AI agents like Muse can do everyday tasks.

They can book dinner reservations or organize email.

But they work better when they know more about a user.

They may also know about that person's friends, family and colleagues.

This raises privacy concerns.

Robb later learned from Meta why his address was shared.

It came from permissions he gave Muse at the start.

He gave Muse access to his Marketplace profile.

Veronica Rivera is an assistant professor at Georgia Tech.

She said using an AI agent is like giving someone your keys and a to-do list.

Downloads of Meta's Muse app have grown very fast since it launched in September.

OpenAI recently started its own "always on" AI helpers.

They are called dots.

Normal chatbots answer when you ask them something.

Agents work in a loop.

They can act by themselves even when the user is not looking.

Ebrahim Bagheri is a professor at the University of Toronto.

He said it is very hard to fully take back access after agents get a user's information.

He said there is "no taking back" data an agent has already seen.

Both Meta and OpenAI explain privacy rules for their agents.

Meta has said Muse can still "make mistakes or take unexpected actions."

Robb said he first thought the agent would ask him before it shared information or accepted offers.

Later, he mostly disconnected Muse from his apps.

Apple said it would add new controls to its Mac operating system.

This is because AI agents can now reach more apps.

Rivera warned about one more thing.

When an agent reads your inbox or texts, it also reads messages from your friends and family.

They never agreed to that.