Composer preview broken in Firefox ESR 17

I know that this is quite an old browser version, but the official specs state that FF 14 is the minimum browser requirement, and one of my clients uses this version. Here’s how the composer window looks in Firefox ESR 17:

Add this to your custom CSS:

/* FF 16+ */
#reply-control .wmd-controls .wmd-input, #reply-control .wmd-controls .wmd-preview-scroller, #reply-control .wmd-controls .wmd-preview {
    -moz-box-sizing: border-box;
    min-height: auto;
#reply-control .preview-wrapper, #reply-control .textarea-wrapper {
    -moz-box-sizing: border-box;

PR open here:


Thanks a million. I guess I will sit and wait if the PR gets pulled. And if not, I will add the CSS!

Just upgraded to the latest Discourse version: works. Thanks all!