Senator Richard Burr (R-NC) walks in the U.S. Capitol in Washington, U.S., August 22, 2018. REUTERS/Joshua Roberts

WASHINGTON (Reuters) - Senator Richard Burr, the Republican chairman of the U.S. Senate Intelligence Committee, said on Wednesday that the “national security vulnerability” and “unacceptable risk” of social media platforms remain unaddressed.

Burr spoke at a committee hearing where top executives from Facebook Inc FB.O and Twitter Inc TWTR.N were testifying on Wednesday about foreign entities' use of social media to influence U.S. political discourse.