What is the ruling on the fasting of one who accidentally came across prohibited images while fasting; is his fast invalidated or flawed? And is a flawed fast acceptable, and how can it be rectified?

Fasting is not invalidated by a forbidden gaze, nor is its reward diminished by a sudden glance if the gazer averts his gaze; he is not sinful for it. However, intentionally repeating the gaze after the first one is a sin. Sins, in general, do not invalidate fasting, but they may diminish its reward or nullify it. Therefore, the fasting person should protect his fast from forbidden acts and sins. The blessing of free time should be utilized for beneficial matters concerning religion and worldly life.