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GitHub projects have recently been under attack with malicious commits and pull requests designed to introduce backdoors into these projects.

One of the latest targets was the GitHub repository of Exo Labs, an AI and machine learning startup. This attack has raised questions about the motives behind it.

On Tuesday, Alex Cheema, co-founder of Exo Labs, alerted others to a seemingly "innocent-looking" code change submitted to the company's GitHub repository. The pull request, titled "clarify mlx requirement for deepseek models," attempted to alter the models.py Python file by inserting a sequence of numbers.

— Backdoor attempt on @exolabs through an innocent looking PR. Read every line of code. Stay safu. pic.twitter.com/M0WHoCF5Mu

These numbers were Unicode representations of characters, effectively encoding the Python code in an obscure format. The sequence "105, 109, 112, 111, 114, 116,..." translates into a code snippet intended to connect to evildojo(.)com and download a "stage1" payload.

If the code change had been accepted and integrated into Exo's repository, users could unknowingly execute code served from this URL, resulting in a potential backdoor in their systems. However, when accessed by BleepingComputer, the link returned a 404 (Not Found), and others reported that the URL never hosted any content.

The situation is complex with no clear resolution. The commit was submitted by a GitHub user named "evildojo666," an account that has since been deleted.

Archived records of the GitHub username and evildojo(.)com point to Mike Bell, a Texas-based security researcher, ethical hacker, and software engineer, who has denied any involvement.

Bell stated that he is being impersonated to tarnish his reputation. He insists, "there was never any payload...why do people keep assuming there was?"

Bell's claims have credibility, as anyone can easily create a GitHub account using someone else's information and images, and then submit code under their name.

The nonexistence of the "stage1payload" page on evildojo's domain also hints that no malicious payload was ever available, suggesting this might be a smear campaign against Bell.

Another GitHub account impersonating Bell, "darkimage666," was identified by Malcoreio, a malware analysis and reverse engineering platform, as being involved in similar malicious activities.

"Not me, an impersonator. Notice account deleted. Very sorry people are being dragged into some skid's beef w/ me," Bell explained regarding the fake account.

Social media users like ChrzanKong observed that other projects were targeted with similar commits from various GitHub accounts.

Threat intelligence analyst vx-underground reported that "yt-dlp," a well-known open-source audio and video downloader, was also targeted. Malcore identified at least 18 similar pull requests directed at other projects.

As of now, BleepingComputer found that many malicious commits and corresponding GitHub accounts, some based in Indonesia, have been removed.

Google engineer and tech events lead, Bogdan Stanga, recreated the pull request to test Presubmit's AI Reviewer. This tool, using GitHub Actions, performs immediate code reviews on incoming pull requests. The test was quickly flagged with a "critical security" alert.

This incident, although contained early, recalls the recent xz supply chain attack, highlighting the risk of malicious code infiltrating popular open-source libraries.

Open-source project maintainers are advised to rigorously review all incoming pull requests using automated and manual methods, regardless of the contributor's perceived intentions.