When I open http://test.m.wikipedia.org/wiki/Testbox#/editor/0 as unregistered user and change something in the text area, the button changes colour, but clicking it does nothing.
I noticed that the HTML is, according to inspector:
<div class="overlay-action"><button class="continue" style="">Next</button></div>
When I login, it's just:
<div class="overlay-action"><button class="continue">Next</button></div>
Can an empty style attribute be at fault?