Developers of Arch Linux discovered three malicious packages in the Arch User Repository (AUR). These packages were used to install the Chaos remote access trojan (RAT) on Linux devices.
The packages were named librewolf-fix-bin, firefox-patch-bin, and zen-browser-patched-bin, and were uploaded by the user danikpapas on July 16, 2025. The packages were removed from the repository two days later, after the community flagged them as malicious.
“On July 16, a malicious package was uploaded to AUR,” warn the AUR maintainers. “Two more malicious packages were uploaded by the same user a few hours later. These packages executed a script from a repository on GitHub, which was identified as a remote access Trojan (RAT).”
As with many other package repositories, there is no formal procedure for reviewing new or updated packages in the AUR. This means that users should independently review the code and installation scripts before building and installing a package.
Although the packages have now been removed, Bleeping Computer examined their archived copies. The PKGBUILD file of all the packages contained a source entry with the name patches, which pointed to a GitHub repository controlled by the attacker: https://github.com/danikpapas/zenbrowser-patch[.]git.
During the processing of PKGBUILD, this repository is cloned and considered as part of the package update and build process. However, instead of a patch, the repository on GitHub contained malicious code that was executed during the build or installation phase. Currently, this repository has been removed from GitHub, and the .git is no longer available for analysis.
The publication also notes that the malware was attempted to be promoted on Reddit through responses to various topics related to Arch Linux (where malicious packages in AUR were promoted in the messages). Comments were posted from an account that had been inactive for many years and was likely compromised and used for “advertising” the malware.
Arch users on Reddit immediately found the comments suspicious, uploaded one of the components to VirusTotal, and discovered Chaos RAT in it.
Chaos RAT is an open-source remote access trojan for Windows and Linux. It can be used for uploading and downloading files, executing commands, and opening a reverse shell. As a result, attackers gain full access to the infected device.
This Trojan is often used in campaigns to distribute cryptocurrency miners, as well as for collecting credentials, stealing information, or espionage.
In this case, after installation, the malware repeatedly connected to the command server 130.162[.]225[.]47:8080, waiting for commands.
“We strongly recommend that users who may have installed any of these packages remove them from their system and take necessary measures to ensure they have not been compromised,” warns the Arch Linux team.
In particular, it is recommended to immediately check for the presence of a suspicious executable file named systemd-initd, which may be located in the /tmp directory. If the file is found, it should be deleted.