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GitHub projects have recently come under threat from malicious commits and pull requests aimed at embedding backdoors into the code. The latest victim is Exo Labs, an AI and machine learning startup, raising concerns over the motivations behind such attacks.

On Tuesday, Alex Cheema, the co-founder of Exo Labs, alerted the community about a seemingly harmless code change in their GitHub repository. The pull request, titled "clarify mlx requirement for deepseek models," tried to alter the `models.py` file by inserting a string of numerical values.

These numbers are Unicode characters, essentially translating the Python code into a numerical representation through a straightforward method applied by the user behind the proposed change. The sequence "105, 109, 112, 111, 114, 116,..." converts into a code snippet that attempts to connect to evildojo(.)com to download a "stage1" payload.

If this change had been integrated into Exo's official repository—which it wasn't—any user could inadvertently execute code served by the URL, effectively planting a backdoor. Upon investigation by BleepingComputer, the link led to a 404 error, with no evidence of previous content at that site.

The situation is perplexing without definitive answers. The commit originated from a GitHub user named "evildojo666," an account now deleted. Archived details connect the username and domain evildojo(.)com to Mike Bell, a Texas security researcher. Bell has consistently denied involvement, suggesting impersonation as a means to sabotage his reputation.

According to Bell, no payload existed, contesting assumptions of its presence. His scenario is plausible as creating a GitHub account mimicking someone else is relatively easy, allowing malicious actions to appear as though they come from another person.

The lack of real content on the evildojo domain hints at a possible character attack on Bell rather than a genuine security breach. Additionally, another removed account, "darkimage666," also impersonated Bell and was linked to similar malicious activities.

Bell responded to the impersonation issue, noting, "Not me, an impersonator. Notice account deleted. Very sorry people are being dragged into some skid's beef w/ me." Meanwhile, other GitHub projects faced similar attacks, using various user accounts as observed by social media users like ChrzanKong.

Threat intelligence analyst vx-underground reported that "yt-dlp," a well-known open-source downloader, was targeted as well. Malcore identified at least 18 similar pull requests made to various projects. BleepingComputer noted that many such malicious accounts and commits, some linked to Indonesia, have since been removed.

Google engineer and tech event organizer Bogdan Stanga replicated the pull request to evaluate Presubmit's AI Reviewer, a tool leveraging GitHub Actions for instant code reviews. The attempt was promptly identified as a "critical security" risk.

Though resolved quickly, this incident reflects tactics seen in the notable xz supply chain attack, where malicious actors infiltrated popular open-source libraries. Open-source maintainers are advised to carefully review incoming pull requests using automated tools and thorough human examination, even from contributors presumed to be acting in good faith.