Is ghusl obligatory upon accidentally seeing something or upon thinking about something and seeking forgiveness for it?

Ghusl is not required merely by seeing or thinking about forbidden scenes. Rather, it is required if semen is discharged. As for madhy (pre-seminal fluid), which is the sticky fluid that is discharged when thinking about lustful matters, it does not necessitate ghusl. However, one must perform istinja’ from it and wash whatever it has soiled on one's clothes. It is obligatory to lower one's gaze from forbidden things and not to indulge in thinking about sexual matters, as these are steps of Satan.