The start dates for the Steam Holiday Sale and Steam Autumn Sale are thought to have been revealed after an image of a "confidential" email appeared online.

The alleged email, which is thought to have been sent by Valve to publishers and developers, states that the Steam Autumn Sale will run from Wednesday, November 27 until Tuesday, December 3, with the Holiday Sale kicking off two weeks later on Thursday, December 19 until Thursday January 2.

"Because the two sales occur just a few weeks apart, we plan to maintain the same discounts from one sale to the other," the email reads.

The image was posted online "by a Russian developer who has a page on Steam Store", a Reddit user alleges, who claims to have received a copy of the email from the leaker as verification.

"Valve is now investigating the leak," the user says.