The active-support ruby gem gem is malware and duplicates the official activesupport (no hyphen) gem, but adds a compiled extension. The extension attempts to resolve a base64 encoded domain (29faea63.planfhntage.de), downloads a payload, and executes.

This trojan horse gem could allow a remote attacker to execute arbitrary code on the system, caused by containing a malicious backdoor. An attacker could exploit this vulnerability to execute arbitrary code on the system. No version of this gem should be considered safe.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-3779
• https://hackerone.com/reports/392311
• GHSA-2j55-pcw5-x4h2