The latest release of the Jenkins plugin that fixed a bug with the url parameter encoding also fixed the authentication issues.

Panic over, ntlm authentication rather than basic authentication required.

What happens if you put the name of a specific artifact? If it were broken, it would be a problem with the extension (which can be easily fixed and published for download pretty quickly). The source code for this particular action is here: https://github.com/Inedo/bmx-jenkins/blob/master/GetArtifactAction.cs

All of these seem valid approaches... #1 obviously has the most flexibility in getting any artifact version. We will soon be releasing an Artifactory Extension that will make Artifactory interactions a little easier.

Thanks, this issue is now fixed after updating the Jenkinds extension to the latest 3.1.2 version.