8 files declare their use of ContentEntityBase

Comment.php in core/modules/comment/src/Entity/Comment.php
ContentModerationState.php in core/modules/content_moderation/src/Entity/ContentModerationState.php
File.php in core/modules/file/src/Entity/File.php
Message.php in core/modules/contact/src/Entity/Message.php
PathAlias.php in core/modules/path_alias/src/Entity/PathAlias.php
Shortcut.php in core/modules/shortcut/src/Entity/Shortcut.php
User.php in core/modules/user/src/Entity/User.php
Workspace.php in core/modules/workspaces/src/Entity/Workspace.php