Bridge Statistics peak

Hi, while flipping through through bridge users statistics, there was phenomena that did not seem natural so thought or reporting because it might be due to a bug (or ti could be just fine)

on a specific data sep 13, 2011 there is a jump up from 200K users to 1M users withing a range of few days and and a similar jump down. What made me doubt is that the peak is distributed across different countries from different continents which seems that it wasn't related to any specific event on the ground. so I thought it could have been a glitch or an attack attempt?! [https://metrics.torproject.org/users.html?graph=bridge-users&start=2011-08-01&end=2011-11-30&country=all&dpi=72#bridge-users]

thanks

Trac:
Username: minarady