Jenkins stores metadata related to people, which encompasses actual user accounts, as well as users appearing in SCM, in directories corresponding to the user ID on disk. These directories used the user ID for their name without additional escaping. This potentially resulted in a number of problems, such as the following:
1. User names consisting of a single forward slash would have their user record stored in the parent directory; deleting this user deleted all user records.
2. User names containing character sequences such as .. could be used to clobber other configuration files in Jenkins.
This is not limited to the Jenkins user database security realm, other security realms such as LDAP may allow users to create user names that result in problems in Jenkins.
Created jenkins tracking bugs for this issue:
Affects: fedora-all [bug 1516794]
Affects: openshift-1 [bug 1516795]