Plarium announces you can not score points for cvc if you join a clan 30min or less before cvc is announced or during cvc. That's only half true. You can not score points for yourself, but you can still score points for the clan. Last week our clan was once more the victim of this trick. We reported it to Plarium with screenshots, now waiting for them to actually DO SOMETHING about it. Here's how it is done :

Both clans start cvc with similar amount of influence, in our case about 1,6t. We take 4 categories, Enemy clan only focusses on killing invaders until 6-8 hours before cvc ends, sometimes earlier. That is when reinforcements join the clan : strong players (lvl 38 or so) that can handle their lvl 3 Tower of Odin - which a merry band of lvl 32-35's never can handle. Suddenly our opponent's influence is 2,7t. We can only sit and watch a single lvl 38 beat every wave. Our attacks were futile. We're just not that strong yet. Sure, the reinfocement can not score points for himself, but he scored 13t points in two categories for the clan. Opponents continue to kill invaders till end of cvc and win. Now you can say we should have gone killing invaders like them, but that is beside the point. We were being cheated. 

Bottom line, any player who joins a clan during cvc can score points during SH Siege, and that should stop. Do something Plarium. We pay for this game. You make sure battles are fair.