Peiter Zatko, aka Mudge, has filed a whistleblower complaint with the SEC against Twitter, claiming that they violated an eleven-year-old FTC settlement by having lousy security. And he should know; he was Twitter’s chief security officer until he was fired in January.
The Washington Post has the scoop (with documents) and companion backgrounder. This CNN story is also comprehensive.
EDITED TO ADD: Another news article. Slashdot thread.