when my county got it's first electronic voting machines, i helped set them up. i can't speak for the security of the process now as i no longer manage the county's IT infrastructure, but nearly 20 years ago, security was paramount.
Discussion
Just a quick search about Pennsylvania mail in ballots.
Need last 4 of your SSN and upload your signature.
Sounds like water tight security these days.
But that still doesn't mean that I can vote twice or vote without being registered.
I will do a mail-in ballot this year if it's not too late to do so.