Mod_auth_openidc.c in the Ping Identity OpenID Connect authentication module for Apache (aka mod_auth_openidc) before 2.14 allows remote attackers to spoof page content via a malicious URL provided to the user, which triggers an invalid request.
https://github.com/pingidentity/mod_auth_openidc/releases/tag/v2.1.4
https://github.com/pingidentity/mod_auth_openidc/issues/212
https://github.com/pingidentity/mod_auth_openidc/commit/612e309bfffd6f9b8ad7cdccda3019fc0865f3b4
https://access.redhat.com/errata/RHSA-2019:2112