Includes fixes for CVE-2021-23953, CVE-2021-23954, CVE-2020-26976, CVE-2021-23960, and CVE-2021-23964. * gnu/packages/gnuzilla.scm (%icecat-version, %icecat-build-id): Update. (icecat-source): Update gnuzilla commit, base version, and hashes. * gnu/packages/patches/icecat-makeicecat.patch: Adapt to new version.