How can Opera browser access my sessions on Google Chrome?

Question

I just installed Opera browser v60 (i.e. Reborn 3) on Windows 10. I noticed that it has automatically (without my consent and permission) taken all my bookmarks in Google Chrome and added to the bookmarks in the Opera browser. In addition, I noticed that somehow it has got access to my open sessions on Google Chrome. By this, I mean that I could for example open some websites using Opera browser without the need to give my username and password since I was logged into them using in Google Chrome browser (e.g. I did not need to login to stackexchange.com).

This felt creepy and made me think how Opera browser can do this? And in general, should I be worried that this happened and change my usernames and passwords?

At the moment, my idea why this happens is that because both browsers are based on Chromium. But I am not sure if this is the reason.

Answer 1

This felt creepy and made me think how Opera browser can do this?

Consider how session cookies are stored. It's stored on disk, as a database of some sort. In Chrome, it appears to be a sqlite database, which is readable by any program running as your user.

The same goes for bookmarks and other user data; it's stored in some form on disk. Accessing it is trivial for any application not specifically sandboxed.

Opera does this to make it easier to switch browser; you get to keep your sessions, bookmarks and history, making a switch almost seamless.

There's no need to change passwords; opera did not do any trickery. Programs that runs on your computer can impersonate you. This is not an unknown side channel or anything, it's fundamentally how computers work.