This module enables you to personalize content for anonymous and authenticated users by showing different blocks to visitors based on client-side conditions.
The Smart Content Block submodule doesn't sufficiently check block access when it renders the blocks of a "Display Blocks" reaction through the module's AJAX endpoint.
This vulnerability is mitigated by the fact that a site must have placed a block whose access is restricted to certain users inside a Display Blocks reaction. Sites that only use Views blocks in reactions are not affected, because Views re-checks access when the view is executed.