Parallels 13 uses cleartext HTTP as part of the update process, allowing man-in-the-middle attacks. Users of out-of-date versions are presented with a pop-up window for a parallels_updates.xml file on the http://update.parallels.com web site.
http://almorabea.net/en/2020/01/19/write-up-for-the-parallel-vulnerability-cve-2020-7213/