Reported in SOLR-14515 (private) and fixed in SOLR-14561 (public), released in Solr version 8.6.0. The Replication handler (https://lucene.apache.org/solr/guide/8_6/index-replication.html#http-api-commands-for-the-replicationhandler) allows commands backup, restore and deleteBackup. Each of these take a location parameter, which was not validated, i.e you could read/write to any location the solr user can access.
{ "nvd_published_at": "2020-08-17T13:15:00Z", "github_reviewed_at": "2021-04-14T18:01:06Z", "severity": "MODERATE", "github_reviewed": true, "cwe_ids": [ "CWE-20" ] }