Asked by Rep. Mike Quigley (D-Ill.) to react to quotes by President Trump and Donald Trump Jr. during the 2016 campaign praising stolen material published by WikiLeaks, special counsel Robert Mueller responded: "Problematic is an understatement."

Why it matters: Throughout his testimony, Mueller has been reluctant to answer questions that stray outside the contents of his 450-page report. His sharp criticism of Trump's praise of WikiLeaks, which he described as an "hostile intelligence service" whose founder Julian Assange is under indictment, is a rare rebuke of the president.

The exchange:

Quigley: "This is Donald Trump, Oct. 10, 2016: 'I love Wikileaks. This Wikileaks stuff is unbelievable. It tells you the inner heart. You got to read it.' Donald Trump, Oct. 12, 2016: 'This Wikileaks is like a treasure trove.' Donald Trump, Oct. 31, 2016: 'Boy, I love reading those Wikileaks.' ... How do you react to it?"

"This is Donald Trump, Oct. 10, 2016: 'I love Wikileaks. This Wikileaks stuff is unbelievable. It tells you the inner heart. You got to read it.' Donald Trump, Oct. 12, 2016: 'This Wikileaks is like a treasure trove.' Donald Trump, Oct. 31, 2016: 'Boy, I love reading those Wikileaks.' ... How do you react to it?" Mueller: "Well, problematic is an understatement in terms of giving some hope or boost to what is illegal activity."

"Well, problematic is an understatement in terms of giving some hope or boost to what is illegal activity." Rep. Quigley: "And Donald Trump Jr. had direct electronic communications with WikiLeaks. On October 3, 2016, WikiLeaks sent another direct message to Trump Jr., asking 'you guys to help disseminate a link alleging candidate Clinton had advocated a drone to attack Julian Assange.' Trump Jr. responded that he had already done so. Same question. This behavior, at the very least, disturbing?"

"And Donald Trump Jr. had direct electronic communications with WikiLeaks. On October 3, 2016, WikiLeaks sent another direct message to Trump Jr., asking 'you guys to help disseminate a link alleging candidate Clinton had advocated a drone to attack Julian Assange.' Trump Jr. responded that he had already done so. Same question. This behavior, at the very least, disturbing?" Mueller: "Disturbing and also subject to investigation."

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