# Version 52.0.0 "Secret For The Mad" 2021-01-04
## New features and enhancements
* MKVToolNix GUI: job queue: the maximum number of jobs to run concurrently
can now be increased in the preferences. The default remains
at 1. Implements #2984.
* MKVToolNix GUI: the GUI will now add a context-specific default extension to
file names selected for saving on platforms that don't add one itself
(e.g. GNOME). For example, when saving multiplexer settings the extension
`.mtxcfg` will be added. Implements #2983.
* MKVToolNix GUI: added an option to the preferences for the window to stay on
top of other windows. Implements #2967.
## Bug fixes
* mkvextract: h.265/HEVC extraction: the code for skipping extraction of
prefix SEI NALUs in the first frame was skipping two bytes too few,
resulting in broken processing of all following bytes. Patch by Mike Chen.
* libEBML: the optional, bundled version of libEBML was updated to v1.4.1.
## Build system changes
* libEBML v1.4.1 is now required due to a bug in libEBML that caused pointers
to just-freed memory being returned to the caller under certain invalid data
constellations, causing use-after-free errors in all of MKVToolNix's
programs. Fixes #2989.