We have heard previous reports of the CIA spying on the Senate Committee that was tasked with overseeing it before, but more information has come to light in the scandal. Senator Dianne Feinstein revealed weeks ago that the CIA had tampered with evidence related to the CIA's torture programs.
New evidence has come to light about the scandal. It has been revealed that not only did they attempt to destroy evidence, but they also continued their efforts to destroy evidence after they were caught initially, and agents lied under oath about their activities.
You can read more about it at: https://www.techdirt.com/articles/20140731/18065928080/cia-spying-senate-went-much-further-than-originally-reported.shtml