Univention Corporate Server 4.3 erratum 546 (security)

This update addresses the following issues:
* Sandbox escape via installation of malicious language pack (CVE-2019-9811)
* Memory safety bugs fixed in Firefox 68 and Firefox ESR 60.8
  (CVE-2019-11709)
* Script injection within domain through inner window reuse (CVE-2019-11711)
* Cross-origin POST requests can be made with NPAPI plugins by following 308
  redirects (CVE-2019-11712)
* Use-after-free with HTTP/2 cached stream (CVE-2019-11713)
* HTML parsing error can contribute to content XSS (CVE-2019-11715)
* Caret character improperly escaped in origins (CVE-2019-11717)
* Out-of-bounds read when importing curve25519 private key (CVE-2019-11719)
* Empty or malformed p256-ECDH public keys may trigger a segmentation fault
  (CVE-2019-11729)
* Same-origin policy treats all files in a directory as having the
  same-origin (CVE-2019-11730)