Group Search on Team Calendars' Restriction Renders Slow

Summary

Group Search popup window once opened in Firefox and IE would only be rendered successfully after a long time (approx. 20++ seconds). The same issue is not observed in Google Chrome browser on reload.

Environment

Tested on:

• Confluence: 5.8.5 and Confluence 5.9.6 - both are vanilla instances.
• Browser: IE 11, Firefox version 43.0.4, v45.0.1 and Chrome version 49.0.2623.110.
• User-base: Confluence Internal Directory with 1 user and 2 users groups (default config).

Steps to Reproduce

1. Navigate to Team Calendars page (<ConfluenceServerBaseURL>/calendar/mycalendar.action)
2. Select Restrictions from one of the existing's Calendar menu.
3. Click Group to apply restrictions to your Confluence's group(s).

Expected Results

The Group Search popup window would be loaded immediately.

Actual Results

Specifically in Firefox and IE web-browsers, the Group Search popup window would only be loaded after approximately 20++ seconds.

Workaround

Disable HTTP Compression under Confluence Admin > General Configuration