[org.geoserver:gs-main] GeoServer allows SSRF via the option for setting a proxy host

GeoServer through 2.18.5 and 2.19.x through 2.19.2 allows SSRF via the option for setting a proxy host.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-40822
• https://github.com/geoserver/geoserver/compare/2.19.2…2.19.3
• https://github.com/geoserver/geoserver/releases
• https://osgeo-org.atlassian.net/browse/GEOS-10229
• https://osgeo-org.atlassian.net/browse/GEOS-10229?focusedCommentId=83508
• https://github.com/advisories/GHSA-rr33-j5p5-ppf8