Apache Solr is an open-source enterprise search platform from the Apache Lucene project. There is a file read vulnerability in Apache Solr, and an attacker can access sensitive information from the target server in unauthorised circumstances. Prior to version 8.8.2, distributed requests were forwarded/proxied using server credentials instead of the original client credentials.
If you are using Solr <= 8.8.1, Upgrade to Solr 8.8.2 or greater. Use another authentication plugin, such as KerberosPlugin or HadoopAuthPlugin.