This is not a bug, you have been auto-promoted. This means you are now in the higher league. When this happens, we place your Alliance in the middle of the pack, so that an Alliance cannot be auto-promoted and end up in 1st position in the higher League without doing anything, and also so that they don’t get Auto-promoted and then just go straight back down. The positive side of this is that you now have a higher chance of gaining better rewards, you don’t have to fight to go up that League.
We understand that this system has its problems; the way that the Leagues work means that we have to ensure that all the seeded Leagues are full for each War, so if an Alliance drops out completely, we auto-promote the top Alliance from the League below and this continues down through the Leagues until the top Alliance in Mortal League is promoted. We did not anticipate it happening so often.
Unfortunately the messaging in-game is not very good for this feature, and also the Alliances which are auto-promoted have one less Blessing than their new opponents. We plan to fix these issues as soon as possible.