On 7th November, 2013, a bug in the system led to a large number of IP users in Europe (and possibly beyond) receiving a notification warning them about an act of vandalism on Aidan Turner (such as this one). Some of the locations affected include:
What had happened is that the vandal edit was registered as coming from 2620:0:862:1:91:198:174:70, which is a Wikimedia cluster server. The server was a newly installed Varnish server that was using an IPv6 address, which the Wikimedia software was not configued to handle properly, resulting in edits being incorrectly attributed by the servers. Because of this, when I proceeded to warn the IP for these edits, a large number of IPs who were browsing Wikipedia at the time received an Orange Bar of Death informing them that they had new messages. When they clicked on this, they were taken to User talk:2620:0:862:1:91:198:174:70 where these warnings were place. Editors were quick to let me know about this both on User talk:2620:0:862:1:91:198:174:70 and on my talk page (with the sum total of 2 trouts and 1 whale!). From reading these messages, I picked up on the following points made by various IPs:
Eventually, both of these talk pages were given a 3 hour semi-block and this put an end to the bombardment of messages from understandably confused IPs. The bug was logged a Bugzilla (the report can be found here) and was reported as fixed by 13:00 (UTC) the next day - just over 14 hours after the incident happened.