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AI data leakage 7 min read

Browser extensions are AI tools too

An extension with read access to every site sees more than most AI services do. We are one ourselves, so this article is about us as well.

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Quick answer

A browser extension with read access to all sites can see the contents of every page you open: your mailbox, your CRM, your case management system and the field you are typing into. That is not a breach; it is the permission granted at installation, usually by the employee. Now that many extensions have added AI features, that reach has grown without anyone taking a new decision. So extensions belong in your inventory of AI use, and the question for each one is the same as for any vendor: what leaves, and who receives it?

01

Read access to all sites means the extension can see every page you open

02

Permissions were granted at installation, usually by the employee alone

03

AI features were added to existing extensions without anyone being asked to approve them again

04

When an extension is acquired, the buyer inherits its installed base

05

Extensions belong in your inventory of AI use

An AI usage inventory almost always produces the same list: ChatGPT, Copilot, Gemini, perhaps Claude. What rarely appears on it are the fourteen extensions installed on the same laptop, four of which have access to all sites and two of which gained an AI feature last year.

This article is about us as well, because we ship a browser extension. That makes it an awkward subject, which is exactly why it is worth writing about.

What "access to all sites" means

When you install an extension, the browser shows which permissions it requests. The broadest is access to your data on all websites. In practice, that means the extension can read the contents of every page you open, and usually change them.

That is a wider reach than most AI services have. ChatGPT sees what you type into ChatGPT. An extension with these permissions sees your webmail, your CRM, your case management system, the intranet and the field you are typing into, whatever site you are on.

No vulnerability is needed for that. It is consent someone gave once, usually within two seconds and usually with no administrator involved.

Three ways this slips out of your control

The permissions stay the same; the function changes. An extension that adjusted colours three years ago gained an AI assistant last year. Its permissions were already broad enough. Nobody was asked to approve anything again, because nothing new was requested.

Acquisitions. A popular extension is bought and the new owner inherits the installed base and the permissions. There are documented cases where that was used to add behaviour the original author never wrote, with automatic updates pushing it to everyone.

The forgotten extension. Installed for one task two years ago, quietly present ever since with full read access.

What the three have in common: the risk does not arise at installation but afterwards, and there is no point at which anyone looks again.

Why this belongs in your AI inventory

If you are mapping which AI services are in use, an extension with an AI feature is an AI service. It processes text, sends it somewhere and has a vendor behind it, with a jurisdiction and terms of its own.

So the questions are the same as for any tool: what leaves, to whom, where is that party based, what is retained and is there a data processing agreement? See approving an AI tool: what to ask the vendor.

The difference is that extensions almost never went through procurement. They arrived the way most shadow AI arrives: through somebody trying to get their work done faster.

What about us?

The BeeSensible browser extension has read access to the pages it works on. If we mean what we have just written, we owe you the same answers about ourselves.

The text you type is analysed to work out what is sensitive. It is sent to our detection service in the EU, analysed in memory and discarded straight away, without being stored. Where the organisation has analytics switched on, we record events without the values themselves: the type of data, the level, the app, the timestamp and the action. No text. When someone visits an AI tool, the extension reports only the domain, at most once per day per device, with no user ID and no page content.

That is the question you should be putting to us, and it is the same question the other thirteen extensions deserve.

Getting a handle on extensions

  1. Take stock. In a managed browser estate you can see which extensions are installed and what permissions they hold. Without central management you are left asking people, which gives an incomplete picture.
  2. Work from an allowlist. Blocking everything does not work, because people need extensions. A short approved list does, provided there is a way to get something added to it.
  3. Reassess when ownership changes. This is the event most often missed.

The reason to put effort into this is not that extensions are more dangerous than other software. It is that they are the only category in which the employee chooses the vendor, approves the permissions and accepts the terms, all in a single click.

FAQ

Common questions

What can a browser extension actually see?

It depends on its permissions. An extension with access to all sites can read the content of every page and usually modify it too. That includes webmail, your CRM, internal applications and the text you type into a field before you send it.

Isn't that a security vulnerability?

No, these are the permissions shown and approved at installation. The problem is that almost nobody reads that screen, and approval happens once, while the extension stays for years and can change what it does.

Why has this become more urgent?

Because many existing extensions added AI features. A writing assistant that used to check spelling locally now sends text to a server to generate suggestions. The permissions did not change; the use made of them did.

What happens when an extension is acquired?

The new owner inherits the installed base and the permissions. There are documented cases of popular extensions being bought and then given behaviour the original authors never included, with automatic updates distributing it to everyone.

How should we handle this?

Take stock of which extensions are in use, assess them as you would any vendor and work from an allowlist rather than a blocklist. Managed browser policies make that enforceable.

Portrait of Rens Timmermans from BeeSensible

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