This werk only affects users with custom bakery plugins that have not been migrated to the new plugin API (introduced in Checkmk version 2.0).
As announced in Werk #11401 the support for legacy bakery plugins (used in Checkmk version 1.6 and earlier) is now dropped.
To see if this affects you, you can grep for the string "bakery_info[" in your local/share/checkmk folder.
Help on how to migrate these plugins can be found in the "Plugin API reference" section of the sites help menu.
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