The correct answer is to assume their encryption doesn’t work and encrypt it yourself. This is true for all cloud storage. Use something like veracrypt.

They had a huge problem with their encryption for a while but I believe it’s now fixed. Additionally, it was ran by Kim Dotcom, the guy who hosted Megadownload, until the New Zealand government took over. So it’s had faulty encryption and is hosted by a 14 eyes government agency. This is why privacy communities recommend alternative options to Mega.

so far i’ve had good experiences with it, definitely not the most privacy focused option out there but they have a decent track record and its cheap. i think the usual advice of not putting anything super sensitive on a cloud storage service still holds, but for most things it should be fine