Threat actors compromised the update infrastructure for Notepad++, redirecting traffic to an attacker controlled site for targeted espionage purposes.

Key takeaways:

1. Beginning in June 2025, threat actors compromised the infrastructure Notepad++ uses to distribute software updates.
    
2. The issue has been addressed and Notepad++ have released 8.9.1 which now includes XML signature validation (XMLDSig) for security updates.
    
3. Reports suggest that the attack was carried out by a Chinese threat actor known as Lotus Blossom.

Background

Tenable’s Research Special Operations (RSO) team has compiled this blog to answer Frequently Asked Questions (FAQ) regarding the disclosure of a supply chain compromise of Notepad++.

FAQ

What happened with Notepad++?

On February 2, Don Ho, creator of Notepad ++, a source code and text editor for Windows, published a blog detailing the investigation into a supply chain security incident.

What kind of security incident is this?

According to the blog post, threat actors compromised the infrastructure by which Notepad++ would distribute software updates. This compromise allowed the attackers to redirect update traffic from its intended destination (notepad-plus-plus dot org) to an attacker-controlled site.

When did this security incident begin?

The security incident began in June 2025.

How long did the security incident last for?

Roughly six months. The compromised infrastructure was accessible until September 2, 2025. However, because the attackers possessed valid credentials for the internal services of the infrastructure provider, they were able to continue redirecting Notepad++ update traffic until December 2, 2025.

Was this incident known prior to February 2?

Yes, Ho published a blog post on December 9 regarding the release of version 8.8.9 and noted that security experts “reported incidents of traffic hijacking affecting Notepad++.” The full scope of the security incident wasn’t known at the time as the investigation was ongoing.

Has this attack been linked to a specific threat actor?

Yes, reports suggest that the attack was carried out by a Chinese threat actor known as Lotus Blossom, also known as Bilbug, Raspberry Typhoon or Thrip.

What do we know about Lotus Blossom?

Lotus Blossom has been operating since 2009, known for deploying various backdoor malware. Regionally, the group has a penchant for targeting entities across Asia including government and the defense sector.

How widespread was this Notepad++ attack?

Despite the widespread usage of Notepad++, reports indicate that Lotus Blossom focused more on espionage of certain targets through the deployment of malware rather than financially motivated cybercrime like ransomware or extortion.

Were there any vulnerabilities associated with this security incident?

No, no CVEs have been assigned for this security incident because the attacks centered on compromising the Notepad++ infrastructure provider and updater.

Are there software updates available for this security incident?

Yes, Notepad++ have released 8.9.1 which now includes XML signature validation (XMLDSig) for security updates with additional signing enforcement expected in version 8.9.2.

Has Tenable released any product coverage for these vulnerabilities?

Yes, a Tenable plugin to identify vulnerable versions of Notepad++ can be found here.

This link will display all available plugins for these vulnerabilities, including upcoming plugins in our Plugins Pipeline.

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