Is it permissible to supplicate for the exposure of the plots and schemes of oppressors and the disclosure of their evil deeds, such as sorcerers, enviers, thieves, and murderers, or is this not permissible on the grounds that Allah has concealed them?

It is permissible to expose and unveil someone who harms Muslims if doing so repels harm from them or makes people wary of them. This is not considered backbiting (gheeba) that is forbidden. Imam An-Nawawi mentioned that the recommended covering of faults (ستر) applies to people of good standing and the like, who are not known for causing harm or corruption. However, for someone known for such behavior, it is recommended not to cover their faults; rather, their case should be referred to the ruler, provided no greater corruption is feared from doing so.