WASHINGTON (Reuters) -A U.S. government data breach disclosed earlier this year was tied to a bug in enterprise software maker Atlassian's Confluence suite of collaboration tools, an IT contractor said on Tuesday.

CGI Federal, an IT contractor and unit of CGI Inc, said in a statement that it was working "with authorities and clients to identify and disclose any data affected by the Confluence exploitation," which was made public back in October.

Reuters has been unable to determine the size and scope of the breach. On Monday, the Government Accountability Office told Reuters that 6,000 current and former GAO employees had been victims of a data breach by an unnamed "threat actor" in connection with the hack. Whether any other government agencies have been affected has not been publicly disclosed.