The first thing people do when their browser slows down is clean up their extensions. However, the real issue with extensions isn’t speed. It’s permissions.
If you re-read the message that appears during installation, it’s already stated quite clearly: “This extension can read and change all your data on all websites you visit.” This isn’t just a warning; it’s a description of its functionality.
How to Interpret Permission Messages
| Displayed Message | Actual Meaning |
|---|---|
| Read and change all your data on all websites | Can read content and modify the screen on any page, including input values. |
| Read and change your data on specific sites | Operates only on that domain. The scope is clearly defined. |
| Change your search settings | Changes the default search engine. Search queries are sent to that provider. |
| Read your browsing history | Accesses the list of visited URLs. |
| Read data you copy and paste | Reads copied content. Passwords are often found here. |
| Manage your downloads | Can download files and determine where they are saved. |
The first row is the most broad. Everything you see on the screen and everything you type falls within its scope. This includes the body of webmails, customer lists in internal systems, and card numbers entered on payment screens.
How Legitimate Extensions Turn Malicious
This is the core issue. There have been repeated instances where extensions that were perfectly safe at the time of installation became problematic later.
1. Acquisitions and Transfers
Developers sell their extensions. Extensions with a large user base are valuable in themselves. Users are not notified even if the new owner changes the code. The extension is quietly replaced via automatic updates.
2. Automatic Updates
Extensions are automatically updated by default. While new permissions require re-consent, extensions that already have broad permissions can change their behavior without additional consent.
3. Loading External Scripts
The installation file itself may be clean, but some are structured to fetch and execute code from an external server during runtime. After passing the initial review, the developer only needs to change the server-side code.
4. Developer Account Hijacking
There have been several cases where a legitimate developer’s account was compromised via phishing, leading to the distribution of malicious versions.
These four scenarios share one thing in common: Your initial judgment at the time of installation does not remain valid indefinitely.
A Step-by-Step Audit Guide
It only takes 10 minutes.
- Open the extension list. Chrome:
chrome://extensions, Edge:edge://extensions - Delete anything you don’t recognize. Any extension you can’t explain why or when you installed it is a candidate for deletion.
- Check ‘Site access’ in each extension’s ‘Details’. If it’s set to “On all sites,” change it to “On specific sites” or “On click.” Most extensions will still function correctly with this setting.
- Look at the developer and the number of users. Extensions with few users or those that haven’t been updated in a long time carry higher risks.
- Separate your work profile. Keep only essential extensions in your work browser profile and do not mix them with personal ones.
Step 3 is particularly effective. Simply narrowing the scope of permissions reduces the potential blast radius in the event of an incident.
Many Extensions Are Unnecessary
It’s common for the same features to already be built into the browser or the operating system.
- Ad and tracker blocking: Browser’s native tracking protection, DNS-level blocking.
- Password management: Native managers in the OS or browser, or dedicated apps.
- Screen capture: Default OS shortcuts.
- PDF conversion and printing: Saving as PDF in the browser’s print dialog.
Removing one extension removes one set of permissions. If the price of a feature is the permission to view every page, it is well worth checking if an alternative exists first.
If You Use Them at Work
A work browser is not a matter of personal preference.
- Operate on an allowlist basis. Set policies so that only approved extensions can be installed.
- AI summarization or auto-writing extensions should be subject to separate review, as they can send internal screens directly to external servers.
- Periodically check for changes in extension ownership and permissions.
Summary
- “Read and change all your data on all websites” is not a warning; it’s an accurate description of functionality. This includes input values.
- Safety at the time of installation is not permanent. Acquisitions, automatic updates, external scripts, and account hijacking are actual pathways for risk.
- Simply changing site access to “On click” significantly reduces the scope of potential damage.
- Delete extensions you don’t recognize. Many features are already built into the browser.
- Manage work browsers using an allowlist, and treat AI extensions that read screens as subjects for separate review.
Frequently Asked Questions
Do many extensions slow down the browser?
Yes, they do. However, the perceived cause is more about the type of extension than the quantity. Extensions that run scripts on every page add a cost to every page load, while those that only run on specific sites have almost no impact. Reviewing permission scopes along with cleaning up will address both speed and security.
Aren’t they safe if they’re in the official store?
They undergo review, but changes made after approval are not continuously filtered. In fact, there have been several reports of extensions turning malicious through updates or ownership changes after passing review. Being listed in the store is a minimum requirement, not a guarantee.
Do extensions work in Incognito/Private mode?
They are disabled by default, but users can allow them. If allowed, they operate with the same permissions in Incognito windows. You can check this for each extension in the settings.
Does deleting an extension also delete its stored data?
Data stored by the extension within the browser is deleted, but any content already sent to external servers remains. If you’ve deleted an extension you used on sensitive pages, it’s safer to change the passwords for those services as well.
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