Linkr allows manifest tampering leading to arbitrary file injection

Summary

Linkr is a lightweight file delivery system that downloads files from a webserver. Linkr versions through 2.0.0 do not verify the integrity or authenticity of .linkr manifest files before using their contents, allowing a tampered manifest to inject arbitrary file entries into a package distribution. An attacker can modify a generated .linkr manifest (for example by adding a new entry with a malicious URL) and when a user runs the extract command the client downloads the attacker-supplied file without verification. This enables arbitrary file injection and creates a potential path to remote code execution if a downloaded malicious binary or script is later executed. Version 2.0.1 adds a manifest integrity check that compares the checksum of the original author-created manifest to the one being extracted and aborts on mismatch, warning if no original manifest is hosted. Users should update to 2.0.1 or later. As a workaround prior to updating, use only trusted .linkr manifests, manually verify manifest integrity, and host manifests on trusted servers.