NOTE: Facebook access to Mixlr is now fully restored. This post is now out of date.
Update 1 (15/9, 3pm London): You can help! Please let Facebook know our domain should be unblocked. You can fill in the URL simply as http://mixlr.com. Thank you for your help!
Update 2 (5.30pm) We are currently still waiting for firm acknowledgement from Facebook. Please keep contacting them through all available means!
Update 3 (8pm) Unfortunately there is no further news to report at this time. We hope the issue will be resolved as soon as possible.
Update 4 (16/9, 9am) No communications have been received from Facebook overnight. We will continue to update this post as we have more news.
Update 5 (10.45am) We’ve put together an FAQ for broadcasters to help you continue to reach your listeners while we wait for a resolution from Facebook.
Update 6 (5pm) We are still waiting for firm contact from Facebook. If you’re broadcasting tonight, check out our FAQ to help you with sharing, logging in and more.
Update 7 (22:45) Facebook access is restored !
This morning we woke up to a number of reports from users of Mixlr links being blocked by Facebook as being “unsafe”.

It soon became apparent that not only was sharing on Facebook not working, but login and signup has also been blocked.

Of course there is no rightful reason why Mixlr should have blocked, so at this time we believe that Facebook’s automated system has erroneously blocked our domain.
Unfortunately, challenging Facebook’s automated decision is not easy. We are currently reaching out to Facebook through all available channels and will update this post as we find out more.