The common site for CSF rhinorrhoea is

The cribriform plate and air cells of the ethmoid sinus account for a maximum number of CSF leaks, i.e., through anterior cranial fossa. Other sites are frontal sinus, an area of sella turcica and sphenoid sinus. Rare sites of the leak are middle or posterior cranial fossa and CSF and reach the nasal cavity by way of the middle ear and Eustachian tubeTraumatic leak-Cribriform plate and ethmoidal air cellsSpontaneous (non-traumatic) leak -Cribriform plateRef: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 183 - 185