[Freak_NL]

More specifically:

https://community.notepad-plus-plus.org/topic/13415/v7-3-3-f...

The CIA replaced a DLL dependency of Notepad++ with a hijacked version on compromised Windows systems.

[creshal]

The dependency is used in a lot of Windows software too, it wasn't even targeted at Notepad++ specifically:

https://en.wikipedia.org/wiki/Scintilla_(software)