How secure something is doesn't only depends on itself but also on its environment. There's a vulnerability known by some which isn't going to be fixed. The moment this vulnerability was disclosed to the FBI, the iPhone became effectively less secure.
More generally, any given version of a piece of software if becoming less and less secure with time, because vulnerabilities are found, although it's the same piece of software.
More generally, any given version of a piece of software if becoming less and less secure with time, because vulnerabilities are found, although it's the same piece of software.