It's just uwu with raised eyebrows. So like, uwu but with surprise or shock. This form of uwu is used online in flirting, texting, and sexting.
guy: wbu, need some more snuggling
girl: mhm and cuddles & kissies pls uwu !
guy: muah uwu, huuug, muah, cmre, muah muah muah
girl: ûwû this is making me curl up in a ball