Exposing aurat is not one of the rukun for valid/invalid ones fast in ramadhan. The fast is valid even though one doesn’t cover her/his aurat. even if youre naked, your fast is still valid. but, the sin is still sin or haram is haram.

It will be written as sinning to Allah. its just we worried because if one doesn’t cover his/her aurat, the mizan will be heavy on the sinning side on the last day, nauzubillah. If that the case, the fasts will be meaningless. The past, lets istighfar.

We ask Allah to accept our ibadah of the past though we did it in the ways that full of defect and haram ways. 

-ustaz azhari idrus(uai)