It's as secure as others promise it to be but actual security is in your own hands. I self-host vaultwarden but I keep it behind a VPN.

The logic is simple, Bitwarden is not there to detect intrusion attempts and safeguard your server so you gotta do it yourself, that's why its free.

You can read the code and see?

I like the spirit of this comment (pointing out that it's OSS). I don't even disagree with discouraging people from asking questions that have readily searchable answers they'd be well served to direct themselves to.

But I think it can be assumed that someone asking such a questions is highly unlikely to be a world-class security researcher equipped to answer it for themselves by auditing the source code, so your response comes across as snarky for the sake of snark.