<p>New features:</p>
<ul><li>When making a new user script, it will include a @match for the current page. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3231">#3231</a>)
<ul><li>Thank you community member Cerberus-tm!</li></ul></li>
<li>Several new features in the built in script editor, most optional (enabled by default). (<a href="http://github.com/greasemonkey/greasemonkey/issues/3230">#3230</a>)</li>
<li>Improved user interface around automatic updates, especially to detect more failure cases and explain them. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3182">#3182</a>)</li></ul>
<p>Fixed bugs:</p>
<ul><li>Do not block script installation when the @icon fails to download. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3222">#3222</a>)</li>
<li>Importing a user script backup that contains a script with a forward slash character in the name should work. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3210">#3210</a>)
<ul><li>Thank you community member nabijaczleweli!</li></ul></li>
<li>Fixed cookie header handling for GM.xmlHttpRequest(). (Previously, it worked only when this was the last header.) (<a href="http://github.com/greasemonkey/greasemonkey/issues/3205">#3205</a>)
<ul><li>Thank you community member syusui-s!</li></ul></li>
<li>Fix partially obscured confirmation dialog when updating an edited script. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3180">#3180</a>)</li>
<li>Improved reliability of script execution at Firefox start up time. (<a href="http://github.com/greasemonkey/greasemonkey/issues/3117">#3117</a>)
<ul><li>Thank you community member binki!</li></ul></li>
<li>Improve GM.xmlHttpRequest() when privacy.firstparty.isolate is true. (<a href="http://github.com/greasemonkey/greasemonkey/issues/2985">#2985</a>)
<ul><li>Thank you community member Scripter17!</li></ul></li>
<li>Fix GM.xmlHttpRequest() when passing functions in the context. (<a href="http://github.com/greasemonkey/greasemonkey/issues/2701">#2701</a>)</li></ul>

New features:

• GM.openInTab() now works in Firefox for Android. (#3189)

<p>Fixed bugs:</p>

• Importing a backup could fail when "overwrite already installed scripts" (enabled by default) was disabled. (#3195)
• Previously unreliable automatic script updates should now work as intended. (#3190)<br />

New features:

• Ability to edit text @resource files. (#2733)
• Support for Firefox on Android. (#3173)

Fixed bugs:

• Code highlighting for newer Javascript features. (#3115)
• An invalid user @match could break opening the monkey menu. (#3171)
• Add a scroll bar when too many menu commands are registered to fit on one screen. (#3177)

New features:

• Support translation for @name and @description of user scripts. (#3089)
• First party support for GM.registerMenuCommand. (#3078)

New features:<br />

• Accessibility enhancements: Appropriate metadata for screen readers, a basic script editor. (#3058, #3059, #3060)

Fixed bugs:<br />

• GM_xmlHttpRequest(): status is null when readyState < 4. (#3068)

Bug fixes:

* Error handling scripts with certain names (bug added in v4.8). (#3035)

Fixed bugs:<br />

• Don't re-enable scripts when saving in editor. (#3008)
• "New user script" doesn't open a new tab. (#2994)
• Log err.message instead of <unavailable> err object. (#2939)

New features:

• Automatic update support (#2531)
• Per-user include/exclude/match settings (#2728)

Fixed bugs:

• Repair GM.xmlHttpRequest() when fetching XML content. (#2980)

New features:

• Added translations in several languages.
• Users may specify global exclude patterns, where no user scripts will run. (#2843)

Fixed bugs:

• Better importing of partial or corrupted backups. (#2966)
• Correctly display script data when switching from one to another. (#2963)
• Correctly display uninstallation of even the last script. (#2957)<br>
• Correctly handle removal of an @icon from a script. (#2910)

New features:

• The script editor interactively downloads newly referenced remote resources, and more clearly handle download errors. (#2858, #2900)

Fixed bugs:

• Scripts with icons or resources could sometimes fail to save, including when only the enabled/disabled status changes. (#2909, #2943)

New features:

• Script editor will prompt, when closing with unsaved edits. (#2886)
• Support for backup and restore of installed scripts. (With very limited support for importing ViolentMonkey and TamperMonkey backups.) (#2747)
• Many improvements to the Monkey Menu. (#2620, #2809, #2833, #2913)

Fixed bugs:

• The open_in_background feature of GM.openInTab() works correctly. (#2672)
• Installation of user scripts works even from sites with strict Content Security Policies, like GitHub. (#2631)

New features:

• Even "forbidden" headers (e.g. Cookie, Host, User-Agent) may be specified when calling GM.xmlHttpRequest(). (#2723)
• Interface strings are translated into multiple languages. (#2527)
• Greasemonkey will not install scripts while disabled. (#2643)
• Monkey menu has new Firefox-native look and feel. (#2805)
• New scalable icon. (#2739)

Fixed bugs:

• Use of the magic TLD is now reflected correctly in the monkey menu user script list. (#2795)<br>
• Privileged API handlers will now refuse to continue without the appropriate @grant entry. (#2777)<br>
• Native xmlHttpRequest now handles URLs relative to the page correctly. (#2771)<br>
• When globally enabling/disabling Greasemonkey, this setting is saved across Firefox restarts. (#2652)<br>

New features:

• Firefox for Android is marked compatible. <br>
• Improved keyboard accessibility of the Monkey Menu. (#2794)
• Added a save button to the user script editor (Ctrl-S still works). (#2785)<br>
• User scripts will execute on local file:///s. (#2693)<br>
• The script install dialog appears in a dialog, not a browser tab. (#2641)<br>
• When the ==UserScript== block contains an unrecognized key, the entire key name is indicated in the warning message. (#2684)<br>

Fixed bugs:

• For GM.xmlHttpRequest, set the finalURL (#2692) and support onprogress (#2712).<br>
• Update @match handling to be consistent with pre-existing behavior.  (#2673, #2715)<br>
• Handle user scripts that end with a comment. (#2670)<br>
• Fix changing @noframes in the user script editor.  (#2637)<br>

New features:

• The "save" action in the user script editor is platform natural.  (#2690)<br>
• Add a "new script" feature, for creating a new user script from scratch.  (#2645)<br>
• The script list in the monkey menu is split into "active" and "inactive" sections.  (#2585)

A complete rewrite from scratch, built on the WebExtensions API to work with Firefox 57 and beyond. For more detail see http://www.greasespot.net/2017/09/greasemonkey-4-announcement.html .