Use of externally-controlled format string in PostgreSQL pg_basebackup allows an attacker having already compromised a server to achieve disclosure from pg_basebackup memory, via backup manifest bytes.  The vulnerability does not return the improperly-read bytes back to the attacker's server, so a successful attack would need separate implementation-specific secrets for that.  Integrity impact is unlikely; in particular, the applicable formatter does not support %n.  Versions before PostgreSQL 18.7, 17.12, 16.16, 15.20, and 14.25 are affected.