Issue Statistics is not working as External Gadget in Confluence

Issue Summary

When adding external gadget "Issue Statistics" from Jira 8.22.0 in Confluence - it is not showing any data

When same Confluence instance is connected to Jira 8.20.6, gadget is working as expected

(tested with Confluence 7.15.0)

This is reproducible on Data Center: (yes) 

Steps to Reproduce

1. Install Jira 8.22.0
2. Install Confluence 7.15.0
3. Setup External Gadgets in Confluence by adding Gadget Feed URL to Jira 8.22.0
4. Create new page in Confluence, click +>Other Macro>Issue Statistics. Configure gadget and click Update

Expected Results

Gadget should be showing data: 

Actual Results

Gadget is not showing any data:

Workaround

1. Stop jira
2. Move <JIRA_INSTALL>/atlassian-jira/WEB-INF/atlassian-bundled-plugins/jira-gadgets-plugin-8.22.0.jar to another (backup) directory
3. Download and copy jira-gadgets-plugin-8.20.6.jarinto <JIRA_INSTALL>/atlassian-jira/WEB-INF/atlassian-bundled-plugins/
4. Start Jira

 It's not clear what is the other potential impact of this WA