This should not change anything noticeable for you in your game. But there is the small possibility that mods you are using may be utilizing the security flaw in a non-malicious way and may therefore stop working with this patch.
If that's the case, you can revert your game version by right clicking the game in Steam -> properties -> BETAS and select the "1.02-no_security_fix..." version. Please note that you do that on your own risk! That version does contain a known security flaw!
Enjoy!
March of the Eagles Security Update
Greetings!
To resolve a security issue tied to the way LUA libraries were loaded for mods we released a minor update. This update will not change your version number or cheksum, and save files should be unaffected.
The update has already been applied through Steam.
To prevent IO or system/OS access in Lua (to prevent mods abusing it), we want to disable the `luaopen_io` and `luaopen_os` functions in the LUA library/dll. These are updated LUA libraries with that functionality disabled.
This does not change behavior of the base game, or impact the multiplayer checksum. Some mods might use these libraries for benign purposes, but unfortunately they will not function after this fix.