When using IE11, we are seeing a recurrence of MDL-19464 / MDL-29680: when completing a form field that contains a text editor (TinyMCE) which is required, you need to submit the form twice. The first time you submit it just tells you the field is required, even though it contains text.

There are no JavaScript errors in the IE11 console when this happens.

We aren't seeing this in other browsers (IE10, Chrome, Firefox).

So far we have tested this on two different Windows 8.1/IE11 machines (poor tester had to walk to another department because we only have one IE11 test machine here) to confirm this does not seem to be machine/installation-specific.

Steps to reproduce:

0. Use IE11 (this doesn't happen in other browsers).
1. Go to http://qa.moodle.net/mod/forum/post.php?forum=2
2. Log in as student/test if required.
3. Wait for the text editor to load.
4. Type in 'test' into the subject field and into the message field.
5. Click the 'Post to forum' button

EXPECTED: The message is posted.

ACTUAL: A 'Required' marker appears next to the form field, and you remain on the form (it hasn't been submitted, this looks like JavaScript code). If you click the Post button again without changing the field, it will then be posted.

We can reproduce this against qa.moodle.net (instructions above) as well as against our OU Moodle 2.4.3+ and 2.5.2+ installs. The problem occurs in standard Forum module (as above) as well as in OU custom modules ForumNG and OU blog, so it doesn't depend on the activity module.

Note: We have applied MDL-42491 to all our systems so it isn't that. IE11 is correctly detected, which we confirmed by looking at the body class= (on one of our systems).

I don't really know much about this area of code so it would be good if somebody else can fix it.