Summary
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Researchers at the University of Wisconsin–Madison have demonstrated that Chrome browser extensions can steal passwords from text input fields, even if the extension is compliant with Chrome’s latest security and privacy standard, Manifest V3.
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They created a proof-of-concept browser extension that could steal passwords and put it through the Chrome Web Store review process.
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The attack works by exploiting the fact that extensions have full and unfettered access to the Document Object Model (DOM) of every web page you visit. The DOM is a representation of a web page in computer memory that can be accessed and changed, allowing the page to be modified on-the-fly.
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The researchers found that most of the top 10,000 websites are vulnerable to this attack, including Google, Facebook, Gmail, Cloudflare, and Amazon.
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They also analyzed the extensions already on the Chrome Web Store and found that 12.5% of them had the necessary permissions to exploit the password input field vulnerabilities.
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The researchers offer two potential fixes: A “bolt on” remedy for vulnerable sites and a “built in” remedy for browsers.
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The bolt on is a JavaScript library that can be added to websites to prevent unwanted access to password fields.
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The built in remedy suggests changing Chrome to alert users whenever any JavaScript function accesses any password fields.
Possible Takeaways / Other Details
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Google have improved security in the Manifest V3 standard, but it’s still possible to sneak in a password stealing extension into the webstore.
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Some/all of the standard’s security improvements may have also been adopted by Microsoft Edge, and Mozilla Firefox.
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It is important to be aware of the risks associated with using browsers’ extensions. Only install extensions from trusted sources and carefully review the permissions that they request.
Most extensions won’t work without access to the DOM, since most extension need to interact with the webpage displayed. I mean what’s the point of being a browser extension if you can’t interact with the web page. The suggestion is to alert when a password field is accessed, maybe an extra permission an extension needs to access the value of a password field. Most extensions don’t need to, for example “dark reader” does not need to know any input field or text node value. So if it suddenly asked for permissions to read my password that would be very suspicious.