v28.5.1 (2019-06-04)
This is a security and bugfix update.

Changes/fixes:
Restored a global getBoolPref() function shortcut for extension compatibility with old extensions.
If you are currently using this global function, please change it to Services.prefs.getBoolPref()
Fixed an issue with the UI when the address bar was removed from the navigation toolbar.
Fixed an issue with scripting of the Help menu.
Fixed a crash resulting from non-standard manipulation of XML stylesheets by extensions.
Fixed browser.link.open_newwindow functionality.
Removed the default handler for webcal since the site doesn't seem to be properly maintained.
Prevented some ways smart places queries could be abused for social engineering attacks.
Ported an upstream Skia fix.
Improved the origin-clean algorithm for canvases.
Improved the efficiency of certain types of memory allocations in the JavaScript compiler.
Changed the way the application update checker code is hooked up so it will not require a user to go idle before being activated.
This solves the primary issue with application updates not notifying users as promptly as they should; more improvements are slated for the next major release.
Applicable security issues fixed: CVE-2019-7317, CVE-2019-11701, CVE-2019-11698, CVE-2019-9817 (DiD), CVE-2019-11700, CVE-2019-11696, CVE-2019-11693,
and several potentially exploitable crashes and memory safety hazards that do not have a CVE number assigned to them.