You know very well that all software has security issues at one point or another, so don't put words in my mouth.
Maybe all software that coders with limited skill sets created have security flaws but in my 35 years of coding NOT A SINGLE ONE of my systems was ever hacked.
Any coder that creates a system "filled with security vulnerabilities" is one lousy coder
Utter nonsense. If you want to bait, don't do it by giving bad advice to novices. The interpretation does not matter. There have been numerous security fixes since 4.1.3, that simply is a fact. Telling someone to not upgrade such an old version bad advice. My guess is you pretty well know that.
Then perhaps you need to make a forum system, so that way it will never require a upgrade.
Now that's an idea. Can't be any worse than the constant security issues found in vBulletin.
What's really striking is that a good number of these flaws are not identified by the staff or even the customers. They're found and exploited by hackers. Does that mean the hackers are smarter than the developers? Maybe the hackers should design the next release.