* Tumblrs that weren't marked adult got marked as such by their new algorithm. This included the text-only official announcement post itself.
* The actual block was done by turning on safe mode for all users, and removing the toggle from the settings page. For a short time, some people were supposedly able to turn in back off by adding that setting back to the POST manually.
* The setting doesn't affect your dashboard, so you can still see new posts by those you follow, even though there's no way to browse to their page directly.
> https://arstechnica.com/information-technology/2019/05/pornh...
However, the porn spambots still keep popping up periodically, and there are still loads of Nazi/alt-right blogs that Tumblr doesn't seem to have any intention of doing anything about.