Security researcher Wladimir Palant, himself an extension developer, decided to look into Screencastify, given its popularity.Įarlier this week, he published what he found.Īmongst other things, his report is a well-written reminder of just how difficult it can be to work out who’s involved in the web of trust you need to have when you decide to use an app or service from company X. The extension boasts 10,000,000+ users (apparently, there is no higher category, no matter how many users you get to), and invites you, in its own description, to: Screencastify is one example of a browser extension that provides a popular feature that wouldn’t be possible via a website alone, namely capturing some or all of your screen so you can share it with other users. Access hardware such as webcams and microphones.Read and write files on your local hard disk.

See and tweak everything you type in or upload before it gets transmitted.

Peek at what is about to be shown in each tab after it’s been decrypted.

Web pages aren’t supposed to be able to override any controls imposed by the browser itself, so they can’t alter the address bar to display a bogus servername, or bypass the Are you sure? dialog that verifies you really did want to download that Word document to your hard disk.īrowser extensions, on the other hand, are supposed to be able, well, to extend and alter the behaviour of the browser itself.Īmongst other things, browser extensions can: …they’d basically just be locally-cached web pages.Īn ad-blocker or a password manager that was locked down so it worked on exactly one website wouldn’t be much use a tab manager that could only manage one tab or site at a time wouldn’t be very helpful and so on. That’s because browser extensions aren’t subject to the same strict controls as the content of web pages you download, otherwise they wouldn’t be extensions… We’ve often warned about the risks of browser extensions – not just for Chrome, but for any browser out there.

Add screencastify to chrome