The Xen Project has published Xen Security Advisories 284, 290, 291, 293, and 294 (XSA-284, XSA-290, XSA-291, XSA-293, and XSA-294, respectively). These XSAs do not affect the security of Qubes OS, and no user action is necessary.

These XSAs have been added to the XSA Tracker:

https://www.qubes-os.org/security/xsa/#284
https://www.qubes-os.org/security/xsa/#290
https://www.qubes-os.org/security/xsa/#291
https://www.qubes-os.org/security/xsa/#293
https://www.qubes-os.org/security/xsa/#294