Try ( after reading about it) Awesome cleaner available at the Dollar Store. My son bought a nice van but the seats were all discolored. When he finished cleaning it with Awesome, the leather upholstery looked like new. Do test in an inconspicuous spot first! Also note Hair spray used to take off ball point pen ink, etc., but the formula has been changed and it no longer works like it used to.

Don't use anything on leather that you would not use to wash your face. Leather is skin and just as touchy to cleaning products. My suggestion, if you can't get a can of saddle soap or another kind of leather cleaner, is to use ivory soap and water (use a damp wash cloth and rinse with a clean cloth, wipe dry).

Hand sanitizer works wonders to get ink off of hands and a lot of other things, but I'm not sure I'd use it on leather. It might dry it out.

Thanks for all the updates! Leather cleaner seems like a safe option. The vehicle has less than 3000 miles on it, and it was just sickening to see what happened, especially since I carefully used a protective cover in the back seats to protect them from kids and pets. Didn't realize I needed one of those myself, but apparently...