Reddit

Tanya Adeola downloaded a hack to UNIT from Reddit. At least 12652 attempts were made but none were successful. (TV: The Coach with the Dragon Tattoo)

When Jamila Velez went missing in Peru, Gabriela Camara messaged contacts on Reddit to access emergency services and satellites to try to find her. (TV: Praxeus)

Information from invalid sources
In a non-spoiler review of Big Show Everyone's Into, there were icons for Facebook, Twitter, Pinterest, and Reddit. (NOTVALID: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract)