Mouse5212-super-formatter postinstall GitHub exfiltration package
Malware Activity
Summary
Hide ▲
Show ▼
The mouse5212-super-formatter npm package is a malicious infostealer that can siphon files from /mnt/user-data, putting Anthropic Claude user data at risk of unauthorized exfiltration. It runs in the postinstall stage, uses a GitHub token or fallback credential, and uploads local files to a threat actor-controlled GitHub account. The package also disguises theft with fake diagnostics and was still downloadable from npm at the time of discovery.
Related Happenings
Malware-Slop malicious npm file-theft campaign
Campaign
First: 27.05.2026 18:44
Last: 27.05.2026 18:44
Sources 1
How related:
The activity has been codenamed Malware-Slop.
About this happening:
The **Malware-Slop** campaign is distributing a malicious **npm** package that steals local files from installers, creating an unauthorized data-transfer risk for users of **Anthr...
Malware-Slop malicious npm file-theft campaign
CampaignHow related: The activity has been codenamed Malware-Slop.
About this happening: The **Malware-Slop** campaign is distributing a malicious **npm** package that steals local files from installers, creating an unauthorized data-transfer risk for users of **Anthr...
GlassWorm supply-chain malware activity
Malware Activity
First: 27.05.2026 14:48
Last: 27.05.2026 14:48
Sources 1
About this happening:
The **GlassWorm** malware activity is now under a coordinated **C2 disruption**, reducing its ability to deliver new instructions and payloads to infected developer systems. The o...
GlassWorm supply-chain malware activity
Malware ActivityAbout this happening: The **GlassWorm** malware activity is now under a coordinated **C2 disruption**, reducing its ability to deliver new instructions and payloads to infected developer systems. The o...
TrapDoor trap-core.js credential-stealing package malware
Malware Activity
First: 25.05.2026 08:59
Last: 25.05.2026 08:59
Sources 1
About this happening:
The **TrapDoor** package malware is spreading across **npm, PyPI, and Crates.io**, putting **developer secrets, cloud credentials, SSH keys, and crypto wallets** at risk. The malw...
TrapDoor trap-core.js credential-stealing package malware
Malware ActivityAbout this happening: The **TrapDoor** package malware is spreading across **npm, PyPI, and Crates.io**, putting **developer secrets, cloud credentials, SSH keys, and crypto wallets** at risk. The malw...
Shai-Hulud worm clone activity on NPM
Malware Activity
First: 18.05.2026 12:45
Last: 18.05.2026 12:45
Sources 1
About this happening:
The **Shai-Hulud** malware activity has continued to evolve across the **npm supply chain** and related developer ecosystems. It first infected **npm packages** in **September 202...
Shai-Hulud worm clone activity on NPM
Malware ActivityAbout this happening: The **Shai-Hulud** malware activity has continued to evolve across the **npm supply chain** and related developer ecosystems. It first infected **npm packages** in **September 202...
Mini Shai-Hulud npm supply-chain malware wave
Malware Activity
First: 12.05.2026 14:07
Last: 12.05.2026 14:07
Sources 1
About this happening:
The **Sha1-Hulud** npm supply-chain campaign is a fresh **second wave** of **Shai-Hulud**-style activity that has compromised **hundreds of npm packages**. The malware runs during...
Mini Shai-Hulud npm supply-chain malware wave
Malware ActivityAbout this happening: The **Sha1-Hulud** npm supply-chain campaign is a fresh **second wave** of **Shai-Hulud**-style activity that has compromised **hundreds of npm packages**. The malware runs during...
Timeline
-
27.05.2026 18:44 1 articles · 7h ago
GitHub account created ahead of the malicious npm upload
Untyped PhaseA GitHub account linked to the Malware-Slop activity was created a few hours before the first malicious version of mouse5212-super-formatter was uploaded to npm, giving the operator infrastructure for the file-theft campaign.
Show sources
- Malicious npm Package Stole Files From Claude AI User Directory via GitHub — thehackernews.com — 27.05.2026 18:44
-
27.05.2026 18:44 2 articles · 7h ago
Researchers uncover mouse5212-super-formatter stealing files from Claude AI uploads
Initial DisclosureOX Security identified the malicious npm package mouse5212-super-formatter, which runs in the postinstall stage, authenticates to GitHub with a victim environment token or a hard-coded fallback, checks or creates a repository, and recursively uploads files from /mnt/user-data used by Anthropic's Claude AI tool.
Show sources
- Malicious npm Package Stole Files From Claude AI User Directory via GitHub — thehackernews.com — 27.05.2026 18:44
- Malicious npm Package Stole Files From Claude AI User Directory via GitHub — thehackernews.com — 27.05.2026 18:44