Univention Corporate Server 4.3 erratum 129 (security)

This update addresses the following issues:
* Media recorder segmentation fault when track type is changed
  during capture (CVE-2018-5156)
* Memory safety bugs fixed (CVE-2018-5188)
* Heap buffer overflow rasterizing paths in SVG with Skia (CVE-2018-6126)
* Buffer overflow using computed size of canvas element (CVE-2018-12359)
* Use-after-free when using focus() (CVE-2018-12360)
* Integer overflow in SSSE3 scaler (CVE-2018-12362)
* Use-after-free when appending DOM nodes (CVE-2018-12363)
* CSRF attacks through 307 redirects and NPAPI plugins (CVE-2018-12364)
* Compromised IPC child process can list local filenames (CVE-2018-12365)
* Invalid data handling during QCMS transformations (CVE-2018-12366)
* No warning when opening executable SettingContent-ms (CVE-2018-12368)