Digital Editions vulnerability patch needed.

According to this security bulleting there is a vulnerability that affects versions 4.5.11.187212 and below.  It says there is a security update that was released but the link to the downloads page is only for version 4.5

11 - no updates.  Where do I get this security update from?   

https://helpx.adobe.com/security/products/Digital-Editions/apsb20-23.html

https://www.adobe.com/solutions/ebook/digital-editions/download.html