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Is the party over for Miley Cyrus and Liam Hemsworth?

Rumor has it that Liam cheated on the "Party in the USA" singer with January Jones at a pre-Oscars party on Febraury 23, according to Us Weekly.

Liam attended the party at the Chateau Marmont hotel in Hollywood without fiancée Miley, and then he shocked the party guests by cozying up to Mad Men star January. 

The source says that when Chris and January were photographed leaving the party, they were headed to another bash, where they were "openly making out." Say it ain't so!

Meanwhile, Miley attended Elton John's post-Oscars shindig by herself on February 24. 

January has had some famous boyfriends over the years, including Ashton Kutcher and Jason Sudeikis. 

In 2011, January gave birth to her son, Xander, but has never confirmed who the baby's father is. She broke up with boyfriend Noah Miller last month. 

Frankly, we find it hard to believe that Liam would cheat on Miley out in the open like this. 

Don't worry, Liam and Miley — we're still rooting for you two!

Source: Us Weekly