Issue on Alerting WebHook since 0.24.0 alertmanager version

What did you do?

I noticed a issue or change of behavior on the latest Alertmanager tag: 0.24.0 on the Receiver Webhook

We are using webhook receiver with a proxy configuration.
This configuration was working fine with Alertmanager 0.23.0
We've upgraded to 0.24.0 and got this issue :

level=error component=dispatcher msg="Notify for alerts failed" num_alerts=1 err="webhook/webhook[0]: notify retry canceled after 2 attempts: Post "https://URL/": Post "https://TOKEN": dial tcp 10.X.X.X:443: connect: connection timed out

Do we need to update the webhook configuration ?

Thanks in advance
regards

  - name: webhook
    webhook_configs:
    - send_resolved: true
      url: "https://URL"
      max_alerts: 4
      http_config:
        proxy_url: "http://PROXY"
        tls_config:
          insecure_skip_verify: true
        oauth2:
          client_id: CLIENT_ID
          client_secret: CLIENT_SECRET
          token_url: https://TOKEN_URL

What did you expect to see?

• Alertmanager version: 0.24.0

• Prometheus version: 2.35.0

Start by reproducing the webhook receiver with the supplied proxy, OAuth2, and TLS configuration on Alertmanager 0.23.0 and 0.24.0, then compare the connection path and errors. Done means identifying whether 0.24.0 requires a configuration change or contains a regression, and documenting the confirmed fix.