Last modified: 2014-03-10 19:37:43 UTC
If you click to use LaTeX, the "math editor" option, you cannot cancel or escape out of input. VisualEditor adds the <math></math> tags regardless and this can only be removed by saving and going to source. Ideally, a cancel [X] or keyboard options should work to remove this. https://www.mediawiki.org/w/index.php?title=User:Keegan_(WMF)/sandbox&action=history
This was fixed a long time ago; sorry for the slow triage.