I imagine that looks pretty bad. On the other hand, Electron apps often aren't running untrusted code, which makes it quite a bit harder to exploit.
I guess an elephant-sized exception to this are the popular code editors that support extensions? Or perhaps such editors’ extensions typically aren’t constrained at all anyway.
Didn't some get exploited early on because electron made it trivial to load third party websites without any kind of XSS protection?
Yep. JavaScript VM breakout, Sandbox breakout and spectre/meltdown side channel leaks are all tracked as vulnerabilities towards Electron while ordinary apps don't even have such security features.