This is the JIRA CVS plugin.

This plugin was created by extracting the existing ViewCVS support from JIRA.

CVS support has been removed from JIRA core as of JIRA 6.1. People who previously
used this feature can continue to do so through the use of this plugin, and data
will continue to work under the new plugin. This plugin is unsupported, however.

Those customers who wish to continue to use CVS within JIRA, whilst receiving
Atlassian's legendary support, are encouraged to migrate to FishEye, or to
migrate away from CVS and to a more recent version control system.