The maintainer of Notepad++ has revealed that state-sponsored attackers hijacked the utility's update mechanism to redirect update traffic to malicious servers instead.
"The attack involved [an] infrastructure-level compromise that allowed malicious actors to intercept and redirect update traffic destined for notepad-plus-plus.org," developer Don Ho said. "The compromise occurred at the hosting provider level rather than through vulnerabilities in Notepad++ code itself."
The exact mechanism through which this was realized is currently being investigated, Ho added.
The development comes a little over a month after Notepad++ released version 8.8.9 to address an issue that resulted in traffic from WinGUp, the Notepad++ updater, being "occasionally" redirected to malicious domains, resulting in the download of poisoned executables.
Specifically, the problem stemmed from the way the updater verified the integrity and authenticity of the downloaded update file, allowing an attacker who is able to intercept network traffic between the updater client and the update server to trick the tool into downloading a different binary instead.
It's believed this redirection was highly targeted, with traffic originating from only certain users routed to the rogue servers and fetching the malicious components. The incident is assessed to have commenced in June 2025, more than six months before it came to light.
Independent security researcher Kevin Beaumont revealed that the flaw was being exploited by threat actors in China to hijack networks and deceive targets into downloading malware. In response to the security incident, the Notepad++ website has been migrated to a new hosting provider.
"According to the former hosting provider, the shared hosting server was compromised until September 2, 2025," Ho explained. "Even after losing server access, attackers maintained credentials to internal services until December 2, 2025, which allowed them to continue redirecting Notepad++ update traffic to malicious servers."
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