The thing is we only know about these vulnerabilities in such great detail because the projects are open source. God knows what kund of vulnerabilities are hidden in closed source software.
Yes, but we don’t know what we don’t know. There are many problems like that in open source too, and even if we can look nobody does.
Therefore I find it problematic to say that just because you use open source programs you’re safe like the parent tried to.
Yes, important to keep in mind that software being open source doesn’t automagically make it secure™.
Still, I think it’s important to stress that the benefits of open source outweigh the risks when it comes to security (imho).