Functionality to upload/login/register is back as of the last few hours. Our devs have implemented a fix and are currently monitoring the site. We'll close this incident in a day or less if everything is all good.
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Why was this functionality impacted?
[full details to be confirmed, however]
A dev apparently had missing characters in the site code. We have a separate test environment for testing changes, however the dev was inspecting an issue that was only on the live site - and could have accidently pressed backspace or similar deleting some code. (😬 wow, yes!)
The incident was fixed around ~35 mins after it was raised. We chose to not restore from a backup as it wasn't needed and lots of people are actively using the site (meaning their stuff could be lost due to a small issue).