Headline is a little misleading imo -- the vulnerability isn't in Notepad++ itself as much as its installer. Current users, I imagine, don't have anything to worry about.
Unless the updater also runs the installer, then you just drop your malicious dll in the right place and wait for an update, or find a way to force-trigger an update.
Attackers can also use the notepad installer as a payload execution mechanism. To run your malware, just get older notepad++ installers and drop your dll after the installer is running to run it as SYSTEM.
For a non-admin user to get admin or system, that's a proper CVE. For an admin user behind uac though, uac bypasses aren't considered bypassing of a security boundary so no CVE there.
Attackers can also use the notepad installer as a payload execution mechanism. To run your malware, just get older notepad++ installers and drop your dll after the installer is running to run it as SYSTEM.