I would like to know the expected value of WCTX parameter so that I could include it in the URL. My Federated application using SAML was working for several months and suddenly it stopped working as the WCTX parameter was missing.
The WCTX parameter is filled outside SiteMinder and it is bound to ADFS. The WCTX parameter is optional, and if you need it, this is because ADFS has been configured to require it. Usually, this parameter has an URL. But this is specific to your architecture, and we have no way to tell you the value it should have. According to Microsoft, the value looks like something as "context data such as a return URL that will be propagated among the different parties" :
Consult the ADFS vendor documentation to get further precisions on this.
Please note also that WS-FED protocol does not support Account Partner initiated Federation :