I think for a while leading up to the recent session stealing hack, there has been a massive amount of positivity from Lemmy users around all kinds of new Lemmy apps, frontends, and tools that have been popping up lately.
Positivity is great, but please be aware that basically all of these things work by asking for complete access to your account. When you enter your Lemmy password into any third party tool, they are not just getting access to your session (which is what was stolen from some users during the recent hack), they also get the ability to generate more sessions in the future without your knowledge. This means that even if an admin resets all sessions and kicks all users out, anybody with your password can of course still take over your account!
This isn't to say that any current Lemmy app developers are for sure out to get you, but at this point, it's quite clear that there are malicious folks out there. Creating a Lemmy app seems like a completely easy vector to attack users right now, considering how trusting everybody has been. So please be careful about what code you run on your devices, and who you trust with your credentials!
Using open source apps, especially with more than one contributor, is currently the best option to be safe from this kind of attack.
Edit: I'm not saying that FOSS is 100% secure because it's FOSS. I'm just saying it's the best option we currently have.
No, because open source apps need to have enough eyes on them to spot malicious code. And highly complex ones need proper audits and even that might not be enough to catch every fancy vulnerability.
I doubt a malicious actor would open source their app tho
That's fair, but sometimes a malicious actor will attempt to covertly contribute code that introduces a security vulnerability.