Prebid Server is an open-source solution for running real-time advertising auctions in the cloud. Prior to version 4.4.0, certain bidder adapters in Prebid Server interpolate user-supplied parameters into outbound request URLs without properly validating host and subdomain values, allowing crafted bid request parameters to cause server-side requests to unintended destinations and potentially expose internal network services or sensitive server endpoints. This issue is fixed in version 4.4.0.
https://github.com/prebid/prebid-server/security/advisories/GHSA-4p3g-4hcj-wpvx
https://github.com/prebid/prebid-server/releases/tag/v4.4.0
https://github.com/prebid/prebid-server/pull/4802
https://github.com/prebid/prebid-server/commit/494ac271cd4b5024df9123ef25ca3cff96390be3