Probably you saw the note from Tim Hall and Julian Frey about the release of the new version of Enterprise Manager 24ai (24.1.0.0.0). It was released on the Oracle edelivery site, but the documentation is not out yet, documentation was released and can be accessed here. But I recommend registering at Oracle Enterprise Manager Technology Forum 2024 to check what it is the new version and what to expect when using the EM 24ai.
Keeping your EM/OMS updated is an essential task to avoid performance and security issues of your monitoring/observability tools. Here you can see the steps to patch your EM from 13.5.0.20 to 13.5.0.24 (the last patch for now). And I also updated the agent running in the EM server to the latest version too.
The main note to check the updates for the EM is Enterprise Manager 13.5 Main Release Update List (Includes Plug-ins) (Doc ID 2760230.2) and this other as well Enterprise Manager Cloud Control Updates: List of Available RUs (Release Updates) and PSUs (Patch Set Updates) (Doc ID 1605609.1). But I prefer this one Enterprise Manager Cloud Control Database (DB) Plug-in 13.5 Release Update (RU) Bug List (Doc ID 2811987.1) because it lists the patches for EM and Agent in one single page (and the solved bug per each version).
From there, we got the links for EM patch 36761595, and Agent patch 36761598. Both they are the RU 24.