There is only one file type that uses the .MXSKIN extension:
Maxthon Skin File
Theme or skin file used by the Maxthon Web browser and introduced with Maxthon version 3 (Maxthon 2 uses .M2S files for skins); contains images and layout settings that customize the appearance of the Web browser.
When you download a new skin, you can double click it to import it into Maxthon. Then, you can change the Web browser's skin by selectingfrom the application menu and choosing a skin from the list.
MXSKIN files are stored in the [user]\AppData\Roaming\Maxthon3\Skins\ directory.
Updated: March 16, 2012