It can happen with ease if OP is browsing the store using his mobile phone. Sometimes when I'm scrolling through the store using my phone my finger accidentally presses the "buy" icon.
Usually it happens with CP2077 because it's the first game to appear on the screen when the main page is loading.

Never hurts to change your password and turn on 2 factor authentication :)

Since it happened to me several times, I'm gonna say that it was due to accidental misclicks. Just being at the home page, the chances of something going to the basket on an accidental click are pretty high. Cyberpunk is there pretty much non-stop and Life is Strange was on sale recently so probably was on the main page too.

It's happened to me several times. The reason: touchscreens can be very tricky!

Unless you have unexplainable completed purchases on your account/credit card, I wouldn't really worry. A hacker who only adds games to the cart but doesn't complete the purchase wouldn't be doing a very good job.

A game got added to my library recently, without any action from me, and yet nothing left my bank account. Explain that. Someone or some AI literally added a game to my library costing approx. $10, but I never got charged.

https://www.gog.com/forum/general/regarding_fahrenheit_indigo_prophecy_remastered_purchase_confirmation_mail

It's a gog glitch (assuming it's Fahrenheit remastered that was added). See banner at top of linked page. Freaked me out too.

https://support.gog.com/hc/en-us?product=gog

Was it Fahrenheit Remastered? This got me this morning too. But the answer is now at the top of the GOG support page:

Important notice! If you received an email confirmation for Fahrenheit Remastered, but did not purchase it, please ignore the email. The game was given for free to all owners of the original Fahrenheit, and these order confirmation emails resulted from a technical issue. We sincerely apologize for the confusion.

So in this case it's just a snafu from GOG giving you a freebie.

Good necro, and your basket or cart is very different to your library.

You should have posted in a different topic, probably your own.

We might be able to help you, if you revealed the game in question, as sometimes we qualify for a free game or remastered version, and several come to mind.

Probably not the best idea to necro post, but was it Fahrenheit? If so - your answer was right there on the first page
https://www.gog.com/forum/general/regarding_fahrenheit_indigo_prophecy_remastered_purchase_confirmation_mail

(heh, apologies, not sure why _I_ didn't see there were other replies)

Sounds similar to a freaky thing that happened to me once. A sneaky spam link once sent me to a foreign version of Amazon and I was logged in as some Indian guy, (if I remember/interpret the name right) completely without any intent on my part. I filled his cart full of expensive Lego and closed the tab without finishing the purchase. Not sure if he had his finances vulnerable enough for me to go all the way, but I just wanted to let this stranger know in the only way I knew how that I was in his account. The Lego obviously would have gone to him anyway.

Maybe the same thing happened with you.

Same here, quite often, I thought it's a portals joke, so I laughed: )
Edit: Never bought a game that way. Freedom is Freedom : )