An issue was discovered in Squid 4.9 through 4.17 and 5.0.6 through 5.6. Due to inconsistent handling of internal URIs, there can be Exposure of Sensitive Information about clients using the proxy via an HTTPS request to an internal cache manager URL. This is fixed in 5.7.
https://www.openwall.com/lists/oss-security/2022/09/23/1
https://github.com/squid-cache/squid/security/advisories/GHSA-rcg9-7fqm-83mq
http://www.squid-cache.org/Versions/v5/changesets/SQUID-2022_1.patch
http://www.squid-cache.org/Versions/v4/changesets/SQUID-2022_1.patch