Well, his sister Stephanie has finally answered it!
To celebrate The Hills' 10th anniversary, Stephanie, Lauren, Heidi Montag, Whitney Port and Brody Jenner are hosting a weekend takeover on MTV.
And ahead of the occasion, Stephanie has been confirming and denying the biggest rumours of the show!
In a new video clip, Stephanie is asked: "Did Spencer start the sex tape rumour about Lauren?" Viewers will easily recall that THAT rumour, which claimed Lauren had appeared in a naughty video with her ex-boyfriend Jason Wahler, was the final nail in the coffin for her friendship with Heidi Montag...
Spilling the beans, Steph replies: "Ok, from the knowledge that I have - which is a lot - the private tape rumour came from the man himself, Jason Wahler, because he tried to sell it.
"Basically, for the show, it got pinned on Spencer and Heidi, because they were talking about it. Jason wasn't on the show anymore."
Stephanie was then asked why Lauren refused to believe that explanation. She explains: "Because she was still mad at them for bringing it up on TV, as I would be too."
Meanwhile, Stephanie is asked if Kristin Cavallari was paid more than the other stars. She reveals: "Kristin was not paid more than all the other cast members. Her starting fee, however, was the same as other's' fees after a few series'. So she came in on the top tier."
Stephanie also reveals Justin Bobby and Holly Montag hooked up off camera, but she refused to discuss her now enemy Roxy Olin, who went on to appear in The City.
We love this game!
Tune into the ultimate The Hills weekend on the 6 and 7 August, only on MTV.
Watch Steph spill the beans here!
The Hills 10 Year Anniversary: Stephanie Pratt On The Biggest Rumours
Watch More: www.mtv.co.uk/the-hills