A regression affecting Adobe Flash Player version 27.0.0.187 (and earlier versions) causes the unintended reset of the global settings preference file when a user clears browser data.
https://helpx.adobe.com/security/products/flash-player/apsb17-42.html
https://euvd.enisa.europa.eu/vulnerability/EUVD-2017-2939
https://access.redhat.com/errata/RHSA-2018:0081