Preview a page that contains special combination of characters fail

Issue Summary

This is reproducible on Data Center: (yes) 

Steps to Reproduce

1. On Confluence page add text that contains the following combination of text

   ../

1. Click Preview

Expected Results

The page is previewed successfully.

Actual Results

Preview fails and the following error notification is seen:

Can't reach the server. Check you're connected to the internet and Confluence is up and running. 

Workaround

Remove the ../ text combination 

Note:

Tested with 7.19.16 and the issue was not seen at this version.