Days after Senate Intelligence Committee members supported greater oversight of social media and Attorney General Jeff Sessions suggested some firms were stifling free speech, Facebook founder Mark Zuckerberg pledged more transparency about security improvements that have been critiqued by Republicans and Democrats alike.

Facebook and Twitter are facing intense congressional pressure to amp up user protections following the 2016 elections, in which the U.S. government said Russian intelligence used the platforms to generate support for President Trump’s campaign. Their efforts have led to claims that security measures are biased against conservative speech, including posts by pro-Trump commentators Diamond and Silk, also known as Lynette Hardaway and Rochelle Richardson.