This is a maintenance release. The following items were fixed and/or added:

- VMM: added support for FSGSBASE, PCID, INVPCID CPU features for guests
- VMM: fixed EMM386 issue with detecting suitable page frame base (bug #10022)
- Front end: Linux: prevent VM window from jumping and auto-resizing to tiny size after resizing it on HiDPI screen
- Front end: Linux: fixed seamless regression caused by wm_class functionality (bugs #12534, #17304)
- Front end: switched to https downloads
- Front end: fixed crash while opening New machine wizard (s.a. forums topic 86592)
- Audio: added support for distinguishing recording sources in the PulseAudio mixer on the host when multiple VMs are running
- Audio: various fixes for the DirectSound backend
- Video recording: added better file seeking support and fixed playback of recorded files with certain players (e.g. Firefox)
- Audio: various fixes for Windows guest surround setups
- Audio: various fixes for HDA emulation
- Serial: fixed an issue where the serial port parameters in the emulation and host serial port got out of sync (bug #17116)
- Storage: fixed overwriting certain INQUIRY data for the DVD/CD drive attached to a AHCI controller
- Storage: fixed handling VMDK images created by Amazon EC2 VM export
- Network: fixed PXE boot regression in e1000
- Network: Added a workaround for older guests which do not enable bus mastering for the virtio PCI device
- 3D: add environment variable to configure presenting 3D content on main thread (see bug #13653)
- Windows hosts: fixed indiscriminate binding of NDIS5 bridged driver, that caused PPPOE malfunction (bugs #16407, #17489)
- Windows guests: fixed incorrect function error when using shared folders in certain applications (bug #14118)
- Linux guests: Linux 4.15 support (bugs #17311, #17320, #17282)
- Linux guests: fixed black screen when 3D enabled in guests (bug #17463, 5.2.6 regression)
- Linux guests: suppress setuid and setgid in shared folders