Univention Corporate Server 4.0 erratum 350 (security)

Firefox ESR 38.3 fixes these issues:
* Memory-safety bugs in NetworkUtils.cpp generally (CVE-2015-4517)
* Memory-safety bugs in ConvertDialogOptions (CVE-2015-4521)
* Overflow in nsUnicodeToUTF8::GetMaxLength can create memory-safety
  bugs in callers (CVE-2015-4522)
* Overflow in nsAttrAndChildArray::GrowBy causes memory-safety bug
  (CVE-2015-7174)
* Overflow in XULContentSinkImpl::AddText causes memory-safety bug
  (CVE-2015-7175)
* Bad sscanf argument in AnimationThread overruns stack variable
  (CVE-2015-7176)
* Memory-safety bug in InitTextures (CVE-2015-7177)
* Mishandling return status in ReadbackResultWriterD3D11::Run might
  cause memory-safety bug (CVE-2015-7180)
* CORS preflight cache poisoning with the credentials flag
  (CVE-2015-4520)
* CORS preflight cache poisoning with a CORS header being mistaken
  with another CORS header
* Information leakage: Dragging and dropping image to <textbox>
  pastes final URL of image after redirects (CVE-2015-4519)
* HTMLVideoElement Use-After-Free Remote Code Execution
  (CVE-2015-4509)
* Heap-buffer-overflow due to overflow in nestegg_track_codec_data
  (MFSA-2015-105)
* maliciously crafted vp9 format video could be used to trigger a
  buffer overflow while parsing the file in vp9_init_context_buffers
  (CVE-2015-4506)
* memory safety problems and crashes that affect Firefox ESR 38.2
  (CVE-2015-4500)
* Heap-buffer-overflow due to overflow in nestegg_track_codec_data
  (CVE-2015-4511)