>>myster+(OP)
Notably Notepad++ was recently shipping unsigned/self-signed updates, apparently overlapping with the time of this incident, see releases 8.8.2-8.8.6: https://notepad-plus-plus.org/news/
>>adzm+d6
You don't even need a certificate to prevent update tampering like this. The updates could have shipped with an ECDSA signature and this wouldn't have happened. It's also free and doable in an afternoon.