Pressing Enter in Message Boards on IE8 moves the cursor down too many lines

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 6.2.X EE
• Fix Version/s: 7.0.0 M4
• Component/s: CKEditor, Message Boards, ~ [Archived] Collaboration
• Labels: None
• Epic/Theme:
  • Escalation
• Story Points: 6
• Fix Priority: 3
• Browsers:
  Chrome (latest), Internet Explorer 8
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/23633

Pressing ENTER in the Message Boards causes multiple new lines to be inserted instead of just one in IE 8

Steps to reproduce

1. Use IE 8.
2. Create a forum.
3. Create a new thread.
4. Navigate to Body and press ENTER for a new paragraph.

Expected result:
Cursor will move down one line.

Actual result:
Cursor will move down multiple lines.

Reproduced

Master =6f4344f43cb1c013c07522044b3ffe79f64a750a (Could not test in Master: currently all admin UI buttons do not work in Master with IE 8)
Branch =0c3127030bb4e2999d2db32320f49912a5c049e4 (Issue reproduced in Branch)