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  • https://www.theregister.com/2025/10/28/ai_browsers_prompt_injection/

AI browsers face a security flaw as inevitable as death and taxes

The Register
·
Avram Piltch
·
Published Oct 28, 2025
·
Updated

Feature With great power comes great vulnerability. Several new AI browsers, including OpenAI's Atlas, offer the ability to take actions on the user's behalf, such as opening web pages or even shopping. But these added capabilities create new attack vectors, particularly prompt injection. Prompt injection occurs when something causes text that the user didn't write to become commands for an AI bot. Direct prompt injection happens when unwanted text gets entered at the point of prompt input, while indirect injection happens when content, such as a web page or PDF that the bot has been asked to summarize, contains hidden commands that AI then follows as if the user had entered them. Last week, researchers at Brave browser published a report detailing indirect prompt injection vulns they found in the Comet and Fellou browsers. For Comet, the testers added instructions as unreadable text inside an image on a web page, and for Fellou they simply wrote the instructions into the text of a web page. When the browsers were asked to summarize these pages – something a user might do – they followed the instructions by opening Gmail, grabbing the subject line of the user's most recent email message, and then appending that data as the query string of another URL to a website that the researchers controlled. If the website were run by crims, they'd be able to collect user data with it. I reproduced the text-based vulnerability on Fellou by asking the browser to summarize a page where I ha...

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Affected Software

3 affected components
Brave Browser
Comet browser
Fellou browser
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Frequently Asked Questions

1

What is the main topic of this article?

The article discusses the security vulnerabilities associated with new AI browsers like OpenAI's Atlas and others.

2

What security implications are discussed in relation to AI browsers?

The article highlights the risk of prompt injection attacks that can exploit the capabilities of AI browsers to perform unintended actions.

3

Which AI browsers are affected by the described security flaw?

The affected AI browsers include Brave, Comet, and Fellou.

4

How do these AI browsers perform actions for the user?

These AI browsers can take actions such as opening web pages or making purchases on the user's behalf.

5

What is the inherent risk mentioned in the context of AI browser capabilities?

The inherent risk is that added capabilities increase the potential for security vulnerabilities and exploitation.

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