Since 1.60, developing missions with certain mods active has unnecessarily added those mods as required for the mission. This includes some very popular mods like CBA, ASR, and ARES. I'm not a mod developer myself but the issue appears to be with mods that modify default units, even if those modifications aren't needed to run the mission.
This is a big problem because you can't edit these missions without having the mods loaded which means you can't fix the offending objects. Right now, the fix is to load the mission in the editor with mods, debinarize the SQM, and delete the unnecessary addons manually. This is a pain to do, and could be a big problem if you have missions that are dependent on mods that you don't have anymore. It also means that you can't edit missions with mods on without the risk of accidentally "infecting" your missions.
This may be a mod issue but it's a big problem right now regardless. And the fact that so many major mods are affected makes me thing it's something that needs to be handled by BI.
(apologies if this is a dupe, the search function isn't great)