Double Bullet Points When Pasting in Editor

In a new page in Confluence, using Firefox version 24.0 and also 25.0:

1. Create a bullet point item.
2. Next line down, add text without a bullet point.
3. Select all text, including the bullet point and non bullet point, copy.
4. Then Paste at the start of the bullet point line.

In Chrome it simply inserts another bullet point line, but in Firefox it puts two bullet points side-by-side.

I've tested in Confluence 4.0, 5.3.0, and 5.3.1, same behaviour in all.

1st attachment is in Firefox, 2nd attachment is in Chrome.