Apple stopped signing iOS 13.2.3 Thursday evening, barely over a week after releasing iOS 13.3 to the general public. It’s an expectable move on the company’s behalf that prevents iPhone and iPad users from restoring to that particular firmware version, or from downgrading from the newer iOS 13.3 release.
Apple’s official reasoning for doing this is to facilitate software upgrades to ensure that users take advantage of the latest features, bug fixes, and security patches. Behind that marketing façade, it’s also evident that Apple prevents software downgrades in an effort to keep the jailbreak community at bay, as most jailbreak tools only operate on older versions of iOS, and Apple quickly patches these jailbreaks in its software updates.