Roger Wardell has/had been leaking info.
So far, much of it is stuff no one can confirm yet.
However, he has said alot things that have been proven true.
These include Falcon, Black Widow, and Crossbones being in Captain America: The Winter Soldier as well as when those two were announced for the film.
Also he leaked Surtur's presence in Thor: TDW, Killian's role in IM3, and that Coulson was not done for in the MCU, alluding to his return beginning in the S.H.I.E.L.D. tv show as well as future movies, as well as Anna Kendrick's candidacy for Sharon Carter
So yeah, he's been credible so far, it's just that people have gotten the idea he's a fraud.
I think Marvel put the hammer down on him though as he hasn't posted anything since the beginning of December.