I have pretty much exhausted all efforts at trying to find information regarding this query on the current forum and others, which is why I'll have to ask here.

Can a dual-national sit for the CSS exam?

This question might sound stupid, however, as you all well know, the online application does not require the applicant to declare his or her nationality - due to the absence of the above aspect, I will hypothesize... a dual national MAY sit for the exam, but renouncing your non-Pakistani affiliation is mandatory upon final stages of Civil service appointment (post-allocation).

Could somebody be kind enough to confirm/clarify the above for me, otherwise correct me if I'm wrong.

I have copied & pasted below, the para pertaining to Nationality in CSS rules and it does not state anything with regards to a candidate's dual-nationality either.

NATIONALITY
6(i). Candidates for the examination must be a citizen of Pakistan or a person deriving his/her nationality from the State of Jammu and Kashmir.

(ii). A candidate who has married a person who is not a citizen of Pakistan shall not be eligible for appointment provided that a person who marries a “foreign national of any country recognized by Federal Government” with the prior permission of Government may be regarded as eligible for appointment.

Thank you for your time.