A subtle but serious security incident has come to light involving a widely used code editor, raising concerns about software update safety.
Notepad++, a popular text and source code editor, has disclosed that its software update system was compromised in a targeted cyberattack. The incident allowed attackers to redirect a limited number of users to malicious servers by interfering with the update process. The breach has now been contained, and additional protections have been put in place.
According to available findings, the attack lasted for several months. The update mechanism was hijacked sometime in June 2025 and remained compromised until early December. During this period, attackers intercepted update requests and selectively redirected some users to malicious servers that delivered altered update information. The timeline of the breach was first reported by a tech news site.
Security researchers noted that the operation was not a broad attack. Instead, it was highly selective and affected only certain systems. Most Notepad++ users were not impacted. Experts involved in the investigation said the level of precision and technical sophistication suggests the attack was likely linked to a Chinese government-aligned hacking group.
The attackers reportedly exploited weaknesses in older versions of the WinGUp update tool used by Notepad++. These versions lacked sufficient verification checks for update files. Hosting provider logs indicate that the server supporting the update application may have been compromised, allowing attackers to manipulate traffic and push malicious update manifests.
The unauthorized activity continued until December 2, 2025, when the hosting provider detected suspicious behavior and shut down the affected connection. Following this, Notepad++ shifted its infrastructure to a new hosting provider with stronger security controls. The development team also rotated exposed credentials, fixed known vulnerabilities, and reviewed system logs to ensure the attack had fully stopped.
To address the issue, Notepad++ released version 8.8.9 in December. This update adds verification for installer certificates and signatures, and ensures update XML files are cryptographically signed. An additional update planned for version 8.9.2 will make certificate signature verification mandatory for all updates.
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