The Federal Trade Commission is investigating Twitter over alleged security and privacy issues, sources said.Shutterstock / rafapress Whistleblower Peiter "Mudge" Zatko's explosive accusations about security concerns at Twitter are almost certain to have sparked a Federal Trade Commission investigation, according to experts - and that's not necessarily good news for Elon Musk.Former FTC officials told The Post they are confident the agency has opened an investigation into Twitter - but added that any potential fine would come after next month's courtroom battle with Musk, potentially requiring the mogul to pony up billions of dollars in penalties if he's forced to take over the company.