Description of problem:

When an invalid URL in an Alertmanager Config: the following logs are present in the prometheus-user-workload pods

26 jun 2025, 12:13:57.796 |   level=error ts=2025-06-26T10:13:57.785124884Z caller=klog.go:126 component=k8s\_client\_runtime func=ErrorDepth msg="sync \\"openshift-user-workload-monitoring/user-workload\\" failed: provision alertmanager configuration: failed to generate Alertmanager configuration: AlertmanagerConfig XXXXX/XXXXX: SlackConfig\[0\]: invalid URL \\"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\\" in key \\"api\_url\\" from secret \\"XXXXXXXXXXXX\\": validate url from string failed for xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: unsupported scheme \\"\\" for URL"
    

With alertmanager enabled for user workload monitoring. This was reported using Slack receiver in alertmanager config

Environment:

User-workload-monitoring, Alertmanager configuration.

Important Notes:
This is an issue with present in Prometheus operator prior to - 0.80.0, for which a fix was implemented: , which is now present in OCP 4.19.

Impact

This issue is impacting customers for example using OCP clusters pre-4.19, especially those with Extended Update support, they remain impacted by this issue for the duration of their support without changing or upgrading to a 4.19 cluster.

Version-Release number of selected component (if applicable):

    4.16.z

How reproducible:

    Easily reproducible on a 4.16 cluster, 

This is a request for this fix from  prometheus operator 0.80.0 to be backported to earlier OCP versions