First entry in table will appear outside of the table when copy pasted in Firefox

Summary

The text in the first row and first column of a copied table will appear outside of the table if you copy paste it while using Firefox.

Environment

• Confluence 5.10.4
• Firefox 49.0 (Current latest version)

Steps to Reproduce

1. Create a new page with a table of size 3x3.
2. Insert dummy text in each row and column.
3. Try to copy paste the entire table underneath the existing table.

Expected Results

The exact table is copy pasted onto the page resulting in 2 identical tables.

Actual Results

The first row and first column of the table appears outside of the table, as seen in the screenshot below.

Notes

This issue is not reproducible in Google Chrome or Internet Explorer 11.