Related to CONF-37262, but the behavior is different in Confluence 6.0 than previous versions.

Summary

After upgrading to Confluence 6.0.x, when creating a web link to an attachment with spaces in the name will link correctly. However, when you link to an attachment when the spaces have already been encoded as '%20', they become '%2520' and are inaccessible. Linking to a URL with '%20' in it did not double-encode the URL in previous versions of Confluence (Tested on Confluence 5.10.8)

Steps to reproduce

1. Start an instance of Confluence 6.0.x
2. Edit a page
3. Choose the link (insert link) icon from the toolbar
4. Enter 'https://sample.com/FY 2017.xls' in the address
5. Change the link text to 'test'
6. Insert
7. Update the page
8. Click on 'test' and it is going to 'https://sample.com/FY%202017.xls' (This is correct)
9. Edit a page
10. Choose the link (insert link) icon from the toolbar
11. Enter 'https://sample.com/FY%202017.xls' in the address
12. Change the link text to 'test2'
13. Insert
14. Update the page
15. Click on 'test' and it is going to 'https://sample.com/FY%25202017.xls' (This is incorrect)

Expected Results

The URL will not double-encode '%20' to '%2520'

Actual Results

The URL is encoded to '%2520' rendering the link incorrect. This does not occur in Confluence version 5.10 and previous.

Workaround

Pasting the original link with '%20' encoding for spaces will work as expected. (Example: https://sample.com/FY 2017.xls )