How to troubleshoot the upgrade/migration issue of Confluence to 7.19.18 and above versions?

This article explains how to resolve the issue encountered with the Polls for Confluence app after you upgrade/migrate to Confluence version 7.19.18 and above.

1. Navigate to the Confluence server installed location at this path: <confluencePath>/atlassian-confluence-7.19.18/confluence/WEB-INF/classes/velocity.properties

2. Do the following changes to the file velocity.properties

   1. Go to introspector.allowlist.classes.

   2. Add com.opensymphony.xwork.util.XWorkList to the existing values on a new line.
      
      Example reference:

      java.io.ObjectInputValidation,\ com.opensymphony.xwork.util.XWorkList,\ net.sf.hibernate.proxy.HibernateProxy

3. Stop and restart the server.