Seriously do you think that for software that manages data the proper way is for someone who starts the upgrade process to say "this is not supported, and now we fucked up your database and you cannot recover from that"? They knew that I was upgrading N+2, this is not a surprise - and I did not realize that upgrading N+2 is not supported.

The proper way would be to abort the upgrade upon discovering that I am going for an unsupported way.

This is not serious software.

I don't understand how commenters here can seriously argue this. There should be no UX for "oh this is not supported? Eh give it a shot anyway, I don't care about literally all my files".

If you don't support upgrading, don't expose that in the UI. There's no excuse for having UI that will let the user do something unsupported and then screw up their data.

Not saying it's the case here, but I wonder how much deniably malicious incompetence out there gets covertly injected into projects by competitors.

That's a very interesting conspiracy theory, I assume the amount is nonzero.

It's risky business, though, as code of course gets reviewed a few times (at least at Nextcloud). If it gets detected once ppl are put on notice. If somebody can squirrel out that the code came from a competitor, a lawsuit is waiting... And just imagine the bad publicity it causes.

Besides that, it is unethical and I wouldn't want to work at a company that pulls such stunts. I think a lot of people wouldn't. It'd be hard to keep secret, too, I mean, 5 years later the employee that was asked to do it works somewhere else and BOOM.

So all together, I think it's extremely unlikely to happen.

I CAN imagine a disgruntled ex employee or angry employee at a competitor would pull something like this. We have seen employees at a competitor create social media sock puppet accounts to spread FUD about us - but management at the competitor put a stop to that once we notified them.