Is it necessary to seek absolution from those who were harmed by denunciation to the occupying power, given the personal and social risks involved in such a disclosure?

Spying on Muslims and conveying their news to enemies is a grave, forbidden sin, for it involves aligning oneself with disbelievers. It is permissible to be outwardly conciliatory towards disbelievers with one's tongue when there is fear of them, while inwardly harboring enmity and refraining from aiding them against a Muslim. Whoever commits this sin must repent to Allah and refrain from informing on a Muslim. He is not obligated to inform those he previously informed on due to the corrupting consequences that would result; rather, he should supplicate for them and increase in benevolence towards them. Allah accepts the repentance of His servant and rejoices in it.