There is always, always a secret change.
I have noticed that when an update comes something will be changed quietly. One time Supercell secretly changed upgrade costs, another time they increased farming restrictions, and this time another one has appeared.
Attachment 4340
Can you see anything different?
Things changed:
1) Goblins suddenly got 10 000 gems and maxxed out their bases
2) The level 8 wall now costs 500k instead of 800k (thats good for me bad for those who gemmed it)
3) Cannons have lost their gold rim in the front (except level 10 ones)
If you have spotted any other secret changes please add them here.