security

Miasma worm shapeshifts, but cloud secret-scouting remains the goal

Microsoft’s GitHub temporarily disabled over 70 repositories after they were reportedly compromised by a worm in the latest open source supply chain attack.

The code shack took down 73 repos within the space of 105 seconds after its alarms were tripped on Friday, June 5, after detecting signs of the Miasma worm infecting its projects, according to StepSecurity’s co-founder and CTO, Ashish Kurmi.

“Our priority is to protect customers and the broader ecosystem. We temporarily removed some repositories as we investigated potential malicious content," a Microsoft spokesperson told us on Wednesday, two days after this story was originally published. "All of these repos have been restored after review. As part of our investigation, we notified a small number of customers who may have pulled down content from the affected repositories. We will continue to investigate, and if anything further is identified that requires customer action, we will reach out directly through our established support channels.”

Users reported issues quickly on Friday, after visits to those repos all resulted in the same message displayed, indicating that they had been disabled due to terms of service violations. 

According to StepSecurity’s analysis, the attack kicked off after a compromised contributor account pushed a malicious commit to Azure/durabletask. The commit dropped configuration files that triggered remote code execution on machines when a developer opened the repo in an IDE or AI coding tool, such as Claude Code, Gemini CLI, and Cursor.

Several developers soon reported broken CI/CD pipelines, a support thread showed, although a moderator said at the time this was due to “an internal management issue.”

"The repo that most immediately caused issues was Azure/functions-action,” Kurmi wrote, used to deploy code to Azure. With it being taken down, every workflow that referenced Azure/functions-action@v1 stopped resolving.

GitHub stepped in a few hours after the repos were infected by the malicious commit. Its automated detections kicked in and disabled the repos in under two minutes, in two separate waves.

However, it was the borking of the durabletask family that hinted at the bigger picture, that the attack was indeed a re-opening of the previous Miasma worm attack that hit Microsoft last month.

Microsoft’s durabletask PyPi package was a previous target of the Miasma worm on May 19. Within a 35-minute window, three versions of the package were uploaded to PyPi, which planted infostealers on developers’ machines, specifically sniffing out cloud secrets and developer tool configurations on Linux systems.

Crucially, the re-targeting of durabletask suggests the tokens associated with the compromised developer account used to execute the PyPi attack were not fully rotated, allowing an attacker to gain access and push commits to GitHub, Kurmi said.

It was either that, or the contributor was re-compromised through the worm's own propagation loop, or a different contributor's token was used but the attacker altered the metadata to make it look like a repeated attack.

Security shop Snyk described Miasma as a descendant of the Mini Shai Hulud worm. It’s the same one that ravaged open source packages over at the npm registry, including Red Hat’s, earlier this month.

Cybercrime group TeamPCP claimed responsibility for developing Mini Shai Hulud, which itself is named after an earlier worm of the same name, sans “mini.” 

However, because TeamPCP open-sourced Mini Shai Hulud, it’s difficult to tell whether it was also behind Miasma or if someone else took the reins on the follow-up project.

StepSecurity also reported that two days before the Microsoft attack, the same worm was making a nuisance of itself at npm, compromising more than 50 packages, including a Vapi.ai SDK with more than 408,000 monthly downloads.®

Updated on June 10 with new comment from Microsoft and the fact that the repos have now been restored.