4. Security – The last and the final stage is the security. This is a serious & time-consuming stage and is done by Canadian Border Services Agency (CBSA) and Canadian Security Intelligence Service (CSIS). Many factors are considered here, such as number of countries visited, applicant country of residence and the political situation there, past law enforcement or military record, prolonged stay in a country with out sufficient documents to prove cause, frequent traveling to certain nations. Upon the completion of the security check by CSIS, the report is submitted to IRCC.
This is ref. to link, even people who do not fall under security criteria still some time they stuck in SS.
