Grzesiek pretty much answered this entire topic.
Now before people get into a moan-fest about CLEO being the cause of the hacked weapons, it has been proven that it is not CLEO on it's own. Something, somewhere along the lines is causing it, but it's not just CLEO or CLEO and ELM by themselves. Someone is either using something they shouldn't, or CLEO is having a conflict with a server script that is causing bugs to arise that lead to this. No other server has reported any issues with CLEO 3 or 4 regarding this, the issues are not present in any version of CLEO, and it's only recently that Argo's SA:MP server has run into this problem, which leads it to prove that it's unique to our server and/or it's players. Again, always use mods at your own risk as Grzesiek said, but people need to also stop assuming that every single person is a hacker just because they use a specific mod. This paranoia is causing users to be banned unknowingly, and it's also leading to users getting angry at the admins for no reason.
If you suddenly think you have hacked weapons, PM an admin immediately and explain to them how it happened so they can help you hunt it down instead of ban you. Until we find the true cause of this, people just need to calm down, be cautious, and stop blaming each other. The rules in this community regarding mods have never changed, so there's no reason to flip out over it now.
The reason it is not reported elsewhere is that on most servers admins do not have the tools we do, or do not care.
It is also possible that somehow CLEO removes the weapons when the player scrolls, and as our detection system is done regardless of scrolling it could trigger non-scrolled but present weapons.
It is not our matter to solve this, if you wish for someone to sort it out connect to SAESAndy who is writing the ELM. He has enough knowledge to solve these kind of things.
As the admins told in the beginning, it is very simple. If you are afraid of mods doing things that may get you banned, do not install them. If you do, do not blame the admins if you do get banned, but remove the mods.
If you are playing and see a big red text that an illegal weapon was removed, LOG OFF and de-activate the mods you have. Either that or wait until you ge banned...