Microsoft have announced End-of-Life for Internet Explorer 9, which is the last version supported by Parallels Containers for Windows:
#123116 Which Internet Explorer versions are supported on Parallels Containers for Windows?
How to keep IE version up-to-date?
Presently, there is no solution other than keeping the outdated version of Internet Explorer on PCW hosts. Parallels are working on allowing IE versions 10/11 to be installed together with PCW in future product updates.