It looks like Guild Wars 2 suffered account rollbacks which affected at least the EU region.
Players noticed this rollback as they saw older characters and accounts upon logging in. In fact, one such player remarked on the timing,
“Based on my rollback of WvW pip progression to gold chest from repeatable one (I played reset night from 18 pm UTC till around 4 am, everything above midnight is gone).
Another player remarked that they lost 100% of their WvW progression since Saturday. It seems ArenaNet is aware of the issue and provided the following statement on their help page,
“We've received many reports of account rollbacks, and are aware of the issue. We've alerted the server team at ArenaNet, and they are working on a resolution.
We will provide updates as soon as we receive more information.
In the meantime, we sincerely apologize for the inconvenience, and thank you for your patience.”
As of right now, we don’t have an indication as to when the issue may be resolved, but the team appears to be investigating.
Additionally, it appears that this rollback is seemingly only affecting EU right now. If you’re in NA, however, you might want to stay offline if you want to be extra careful.