A rapidly spreading malware campaign has infected hundreds of software packages across major open-source registries, embedding credential-stealing code into development tools downloaded millions of times a week.
The attack, referred to as “mini Shai-Hulud,” targeted prominent software libraries, including TanStack, UiPath, and MistralAI. TanStack’s React Router package alone accounts for more than 12 million weekly downloads, placing the malicious code deep within the software supply chain of modern enterprise applications.
In a blog post, Tanstack said security teams have pulled all compromised software versions from the registry. While there is no evidence that registry passwords were stolen, experts urge anyone who downloaded the affected tools Monday to immediately change all connected cloud, server, and developer credentials — including Amazon Web Services, Google Cloud, and GitHub.
The incident highlights a systemic vulnerability in automated software publishing. The compromised updates successfully bypassed two-factor authentication and carried cryptographically valid provenance signatures. These signatures verified that the packages originated from the correct continuous integration pipelines, but failed to detect that the pipelines themselves had been manipulated to authorize malicious code.
Security researchers attribute the campaign to TeamPCP, a cloud-focused cybercriminal group that emerged in late 2025 that specializes in automating supply-chain attacks and exploiting cloud-native infrastructure, including Docker and Kubernetes environments. The group, alleged to be responsible for earlier development of Shai Hulud, quietly slips their malware into trusted software updates, allowing them to infect thousands of companies at once without triggering security alarms.
The group is notorious for its advanced ability to hide its tracks — such as disguising stolen data as anonymous messaging traffic — and its aggressive extortion tactics, which include threatening to completely erase victims’ computers if they attempt to remove the hackers’ access.
Attackers triggered the automated release process using an “orphaned commit” — code pushed to a repository fork without a corresponding branch. This allowed them to exploit overly broad permissions in GitHub Actions workflows. The malware was then delivered via a concealed dependency that fetched a heavily obfuscated 2.3-megabyte payload disguised as an initialization module.
Upon execution, the malware uses Bun — a high-speed software engine designed to run JavaScript — to systematically steal security keys and passwords. It targets high-level cloud infrastructure, including AWS, Google Cloud Platform, Kubernetes, and HashiCorp Vault. The code is engineered to infiltrate highly secure Amazon cloud networks. At the same time, it scours the developer’s local computer for secret files and SSH keys used to unlock other corporate systems.
Operating as a self-propagating worm, it publishes copies of itself to those projects, spoofing its activity to appear as automated commits from the Anthropic Claude bot. In a secondary extortion measure, the malware generates a new registry token containing a ransom note in its description, threatening a destructive computer wipe if the victim attempts to revoke the compromised access.
Despite the malware’s properties, researchers told CyberScoop they have not seen it spread.
“We saw very limited community spread,” said Charlie Eriksen, a security researcher with application security firm Aikido Security.
To maintain continuous access to developer workstations, the malware embeds itself into the configuration files of popular developer tools, notably Visual Studio Code and Anthropic’s Claude Code. This ensures the malicious scripts execute automatically every time a developer opens a project or initiates an AI coding session.
Stephen Thoemmes, senior developer advocate at Snyk, told CyberScoop this is a particular blind spot for these types of attacks.
“Directories like .claude/ and .vscode/ are typically excluded from version control via .gitignore and are rarely scrutinized as viable attack surfaces,” Thoemmes said. “While these hook and task systems provide valuable automation for legitimate work, they offer a silent execution environment for malicious code. To counter this, developers must move away from treating these local configurations as benign and begin applying the same rigorous security auditing to their tooling directories as they would to their production infrastructure.”
To avoid detection, the stolen data is exfiltrated using Session — an anonymous messaging app that bounces data across a decentralized network. By disguising the theft as ordinary, encrypted chat traffic, the hackers blend in with normal network activity. This allows the attackers to completely ditch the traditional “command” servers that corporate security teams usually hunt for and block.
The success of the “Mini Shai-Hulud” campaign exposes a major blind spot in software security: Current defenses check where an update comes from, but not if the code inside is actually safe. By hijacking the developers’ own automated systems, attackers were able to stamp their malware with official digital signatures — proving that attackers can bypass modern safeguards simply by turning a company’s own tools against them.
Socket CEO Feross Aboukhadijeh told CyberScoop that organizations should look for signs that a compromised package version was installed in CI/CD or developer environments, unexpected outbound connections to campaign infrastructure, suspicious changes in package lockfiles, unusual package publishes from their own maintainers or CI systems, and persistence artifacts in developer tooling directories.
“There is no single centralized kill switch for this kind of campaign,” Aboukhadjieh said. “The hard part is that by the time a malicious package is confirmed, it may already have been installed inside the exact environments attackers want most: developer machines and CI runners. You can pull a package from the registry, but you cannot automatically pull back the credentials it may have already stolen.”
While these packages are maintained by volunteers, Eriksen said the incident is a huge issue for enterprises due to how many development teams use the software in their products and services.
“This is not a ‘volunteer’ vs corporate thing,” Eriksen told CyberScoop. “This is an all-of-society problem.”
Aboukhadjieh told CyberScoop that these continuing attacks on popular open-source software packages is part of “a larger reckoning over how the software industry consumes open source.”
“This campaign shows how thin the line has become between a developer tool and critical infrastructure,” he said. “When attackers compromise tools that are already trusted inside build systems, they do not have to break into every company directly. They can ride the trust those tools already have.”
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