Opencast still publishes global system account credentials
### Description
Opencast prior to versions 17.6 would incorrectly send the hashed global system account credentials (ie: `org.opencastproject.security.digest.user` and `org.opencastproject.security.digest.pass`) when attempting to fetch mediapackage elements included in a mediapackage XML file. A previous CVE
https://github.com/opencast/opencast/security/advisories/GHSA-hcxx-mp6g-6gr9 prevented many cases where the credentials were inappropriately sent, but not all. The remainder are addressed with this patch.
### Impact
Anyone with ingest permissions could cause Opencast to send its hashed global system account credentials to a url of their choosing.
### Patches
This issue is fixed in Opencast 17.6
If you have any questions or comments about this advisory:
- Open an issue in our issue tracker
https://github.com/opencast/opencast/issues
- Email us at
security@opencast.org