The Cybersecurity and Infrastructure Security Agency (CISA) said Monday that there is “no indication” other federal agencies were impacted by the recent breach at the Treasury Department.  The Treasury Department revealed last week that Chinese state-sponsored actors had hacked into the agency’s workstations in early December and accessed unclassified documents.   The hackers obtained a key from a third-party software service provider, BeyondTrust, which they used to override security and gain access to Treasury workstations, the agency said in a letter to lawmakers.  CISA said in a statement Monday that it is “working closely” with both the Treasury and BeyondTrust to “understand and mitigate the impacts” of the breach.  “The security of federal systems and the data they protect is of critical importance to our national security,” the federal cyber watchdog added. "We are working aggressively to safeguard against any further impacts and will provide updates, as appropriate.”  The Treasury Department has promised to provide an update to lawmakers in 30 days as required by law.  However, the incoming chairs of the Senate Banking Committee and House Financial Services Committee, both of which oversee the agency, asked Treasury Secretary Janet Yellen on Tuesday for a briefing on the incident by Jan. 10.  “This breach of federal government information is extremely concerning. As you know, Treasury maintains some of the most highly sensitive information on U.S. persons throughout government, including tax information, business beneficial ownership, and suspicious activity reports,” Sen. Tim Scott (R-S.C.) and Rep. French Hill (R-Ark.) wrote.  “This information must be vigilantly protected from theft or surveillance by our foreign adversaries, including the Chinese Communist Party (‘CCP’), who seek to harm the United States,” they added.