diff --git a/README.md b/README.md
index 91b090e..3f788f1 100644
--- a/README.md
+++ b/README.md
@@ -503,10 +503,12 @@ Markdown formatting is controlled by the following filters:
 
   The current default extensions are:
 
-  * [`League\CommonMark\Ext\Table\TableExtension`](https://github.com/thephpleague/commonmark-ext-table#syntax), which implements Markdown tables,
-  * [`Webuni\CommonMark\AttributesExtension\AttributesExtension`](https://github.com/webuni/commonmark-attributes-extension#syntax), which allows adding Kramdown-style HTML attributes to blocks and spans, and
-  * [`League\CommonMark\Ext\Strikethrough\StrikethroughExtension`](https://github.com/thephpleague/commonmark-ext-strikethrough/#readme), which turns `~~`-wrapped text into `<del>` elements for strikethrough, and
-  * [`League\CommonMark\Ext\SmartPunct\SmartPunctExtension`](https://github.com/thephpleague/commonmark-ext-smartpunct#readme), which translates dots and hyphens to ellipses and em/en dashes, and converts plain single and double quotes to their left/right versions.
+  * [`League\CommonMark\Extension\Table\TableExtension`](https://commonmark.thephpleague.com/1.6/extensions/tables/#syntax), which implements Markdown tables,
+  * [`League\CommonMark\Extension\Attributes\AttributesExtension`](https://commonmark.thephpleague.com/1.6/extensions/attributes/#attribute-syntax), which allows adding Kramdown-style HTML attributes to blocks and spans,
+  * [`League\CommonMark\Extension\Strikethrough\StrikethroughExtension`](https://commonmark.thephpleague.com/1.6/extensions/strikethrough/), which turns `~~`-wrapped text into `<del>` elements for strikethrough,
+  * [`League\CommonMark\Extension\SmartPunct\SmartPunctExtension`](https://commonmark.thephpleague.com/1.6/extensions/smart-punctuation/), which translates dots and hyphens to ellipses and em/en dashes, and converts plain single and double quotes to their left/right versions,
+  * [`League\CommonMark\Extension\Autolink\AutolinkExtension`](https://commonmark.thephpleague.com/1.6/extensions/autolinks/), which supports [Github-style autolinking](https://github.github.com/gfm/#autolinks-extension-) of bare URLs and web hostnames,
+  * [`League\CommonMark\Extension\TaskList\TaskListExtension`](https://commonmark.thephpleague.com/1.6/extensions/task-lists/), which adds support for [Github-style task lists](https://github.github.com/gfm/#task-list-items-extension-),
   * `dirtsimple\Postmark\ShortcodeParser`, which detects lines that consist solely of shortcode opening or closing tags, and passes them through without markdown interpretation.  (This allows you to enclose markdown blocks within a shortcode, instead of having the shortcode become part of the block itself, which can be problematic when using e.g. conditional tags.)
 
 * `apply_filters('postmark_markdown', string $markdown, Document $doc, $fieldName)` -- this filter can alter the markdown content of a document (or any of its front-matter fields) before it's converted into HTML.  `$fieldName` is `"body"` if `$markdown` came from `$doc->body`; otherwise it is the name of the front matter field being converted.  (Such as `"Excerpt"`, or any custom fields added by plugins.)
diff --git a/composer.json b/composer.json
index a1d0f2a..c604bff 100644
--- a/composer.json
+++ b/composer.json
@@ -33,16 +33,12 @@
     "require": {
         "dirtsimple/clean-yaml": "^0.1",
         "dirtsimple/imposer": "dev-master",
-        "wp-cli/wp-cli": "^2",
-        "wp-cli/entity-command": "^2",
+        "wp-cli/wp-cli": "^2.11",
+        "wp-cli/entity-command": "^2.8",
         "rarst/wpdatetime": "^0.3.0",
-        "league/commonmark": "^1.0",
-        "league/commonmark-ext-smartpunct": "^1.1",
-        "league/commonmark-ext-strikethrough": "^1.0",
-        "league/commonmark-ext-table": "^2.1",
-        "webuni/commonmark-attributes-extension": "^1.0",
+        "league/commonmark": "^1.6",
         "twig/twig": "^2.4",
         "symfony/yaml": "^3.4",
-        "php": "^7.1"
+        "php": ">=7.1"
     }
 }
diff --git a/src/Formatter.php b/src/Formatter.php
index 6e04cc5..452ce62 100644
--- a/src/Formatter.php
+++ b/src/Formatter.php
@@ -27,10 +27,12 @@ protected static function formatter() {
 				'line_break' => "",
 			),
 			'extensions' => array(
-				'League\CommonMark\Ext\Table\TableExtension' => null,
-				'Webuni\CommonMark\AttributesExtension\AttributesExtension' => null,
-				'League\CommonMark\Ext\Strikethrough\StrikethroughExtension' => null,
-				'League\CommonMark\Ext\SmartPunct\SmartPunctExtension' => null,
+                'League\CommonMark\Extension\Autolink\AutolinkExtension' => null,
+                'League\CommonMark\Extension\Table\TableExtension' => null,
+                'League\CommonMark\Extension\TaskList\TaskListExtension' => null,
+				'League\CommonMark\Extension\Attributes\AttributesExtension' => null,
+                'League\CommonMark\Extension\Strikethrough\StrikethroughExtension' => null,
+				'League\CommonMark\Extension\SmartPunct\SmartPunctExtension' => null,
 				'dirtsimple\Postmark\ShortcodeParser' => null,
 			),
 		);
diff --git a/src/Option.php b/src/Option.php
index 9a20370..74ef240 100644
--- a/src/Option.php
+++ b/src/Option.php
@@ -1,8 +1,8 @@
 <?php
 namespace dirtsimple\Postmark;
 
-use WP_CLI\Entity\RecursiveDataStructureTraverser;
-use WP_CLI\Entity\NonExistentKeyException;
+use WP_CLI\Traverser\RecursiveDataStructureTraverser;
+use WP_CLI\Exception\NonExistentKeyException;
 use WP_CLI;
 
 class Option {