Vault 7: CIA Hacking Tools Revealed" has been published by Wikileaks recentely, and Notepad++ is on the list.
The issue of a hijacked DLL concerns scilexer.dll (needed by Notepad++) on a compromised PC, which is replaced by a modified scilexer.dll built by the CIA. When Notepad++ is launched, the modified scilexer.dll is loaded instead of the original one.
More infos and download can be found
here