A vulnerability in urllib3 versions 1.26.0 through 2.7.0 causes HTTPS proxy TLS configurations to be ignored or overridden by the target server's TLS settings. This can lead to disabling certificate verification for the proxy connection or applying target-specific TLS parameters to the proxy connection, potentially allowing an attacker intercepting the proxy connection to impersonate the proxy and access sensitive data. The issue is fixed in urllib3 version 2.8.0.