CNNMoney: On Thursday, Twitter experienced its most significant outage since last October 7. The outage began at 11:59 a.m. ET. By 1:00 p.m., service was beginning to come back online, but then Twitter went dark again. Twitter didn't completely resolve the issue until around 3:00 p.m.
Hackers from UGNazi claimed to be behind the outage, but Twitter said it was caused by "a cascaded bug in one of our infrastructure components."