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On the logout page the iFrame is rendered with logout request to external provider. It should contain id_token_hint.
Cleanup
During logout we remove id_token that was used as it is not needed anymore. There will be situations when these tokens won’t be removed as no logout was invoked (like when browser simply closed). That means there will be obsolete id_tokens hanging in our cache.
To clean them up there is a process that you can set up using 131, 132 settings Settings .