Those cameras are not equipped with recording capabilites but merely used to monitor the cabin during takeoff/landing/turbulence while cabin crew are seated themselves and cannot see the aisles.Those are not 'security cameras' but 'safety monitors'.
No commercial airline has security cameras in their cabins where footage is retained.

edit: This has been discussed on here several times over the years. See this thread, for example: First Cabin CCTV Camera on A380