This was caused by a hardware failure in one of the many Power Distribution Units on the rack where our main server is hosted. Riseup, also hosted in the same datacenter, suffered from the [same hardware failure](https://twitter.com/riseupnet/status/1388214079316283394).
Some of you were afraid that the Tails infrastructure could have gone under an attack of some sort. This does not seem to have been the case. The actual reasons for the power glitch are still being investigated, but all indicates that it was a simple hardware failure. There are no signs of malicious activity whatsoever.