diff --git a/package-lock.json b/package-lock.json
index 861a8bf..b1b3adf 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -536,7 +536,7 @@
       "dependencies": {
         "load-json-file": {
           "version": "2.0.0",
-          "resolved": "http://registry.npmjs.org/load-json-file/-/load-json-file-2.0.0.tgz",
+          "resolved": "https://registry.npmjs.org/load-json-file/-/load-json-file-2.0.0.tgz",
           "integrity": "sha1-eUfkIUmvgNaWy/eXvKq8/h/inKg=",
           "dev": true,
           "requires": {
@@ -1458,12 +1458,6 @@
         "convert-to-spaces": "^1.0.1"
       }
     },
-    "code-point-at": {
-      "version": "1.1.0",
-      "resolved": "https://registry.npmjs.org/code-point-at/-/code-point-at-1.1.0.tgz",
-      "integrity": "sha1-DQcLTQQ6W+ozovGkDi7bPZpMz3c=",
-      "dev": true
-    },
     "collapse-white-space": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/collapse-white-space/-/collapse-white-space-1.0.3.tgz",
@@ -2509,12 +2503,14 @@
         "balanced-match": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "brace-expansion": {
           "version": "1.1.11",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "balanced-match": "^1.0.0",
             "concat-map": "0.0.1"
@@ -2529,17 +2525,20 @@
         "code-point-at": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "concat-map": {
           "version": "0.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "console-control-strings": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "core-util-is": {
           "version": "1.0.2",
@@ -2656,7 +2655,8 @@
         "inherits": {
           "version": "2.0.3",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "ini": {
           "version": "1.3.5",
@@ -2668,6 +2668,7 @@
           "version": "1.0.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "number-is-nan": "^1.0.0"
           }
@@ -2682,6 +2683,7 @@
           "version": "3.0.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "brace-expansion": "^1.1.7"
           }
@@ -2689,12 +2691,14 @@
         "minimist": {
           "version": "0.0.8",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "minipass": {
           "version": "2.2.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "safe-buffer": "^5.1.1",
             "yallist": "^3.0.0"
@@ -2713,6 +2717,7 @@
           "version": "0.5.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "minimist": "0.0.8"
           }
@@ -2793,7 +2798,8 @@
         "number-is-nan": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "object-assign": {
           "version": "4.1.1",
@@ -2805,6 +2811,7 @@
           "version": "1.4.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "wrappy": "1"
           }
@@ -2926,6 +2933,7 @@
           "version": "1.0.2",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "code-point-at": "^1.0.0",
             "is-fullwidth-code-point": "^1.0.0",
@@ -4417,9 +4425,9 @@
       }
     },
     "opn": {
-      "version": "5.4.0",
-      "resolved": "https://registry.npmjs.org/opn/-/opn-5.4.0.tgz",
-      "integrity": "sha512-YF9MNdVy/0qvJvDtunAOzFw9iasOQHpVthTCvGzxt61Il64AYSGdK+rYwld7NAfk9qJ7dt+hymBNSc9LNYS+Sw==",
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/opn/-/opn-6.0.0.tgz",
+      "integrity": "sha512-I9PKfIZC+e4RXZ/qr1RhgyCnGgYX0UEIlXgWnCOVACIvFgaC9rz6Won7xbdhoHrd8IIhV7YEpHjreNUNkqCGkQ==",
       "requires": {
         "is-wsl": "^1.1.0"
       }
@@ -6282,33 +6290,14 @@
         "string-width": "^2.1.1"
       },
       "dependencies": {
-        "is-fullwidth-code-point": {
-          "version": "1.0.0",
-          "resolved": "https://registry.npmjs.org/is-fullwidth-code-point/-/is-fullwidth-code-point-1.0.0.tgz",
-          "integrity": "sha1-754xOG8DGn8NZDr4L95QxFfvAMs=",
-          "dev": true,
-          "requires": {
-            "number-is-nan": "^1.0.0"
-          }
-        },
         "string-width": {
-          "version": "1.0.2",
-          "resolved": "https://registry.npmjs.org/string-width/-/string-width-1.0.2.tgz",
-          "integrity": "sha1-EYvfW4zcUaKn5w0hHgfisLmxB9M=",
-          "dev": true,
-          "requires": {
-            "code-point-at": "^1.0.0",
-            "is-fullwidth-code-point": "^1.0.0",
-            "strip-ansi": "^3.0.0"
-          }
-        },
-        "strip-ansi": {
-          "version": "3.0.1",
-          "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-3.0.1.tgz",
-          "integrity": "sha1-ajhfuIU9lS1f8F0Oiq+UJ43GPc8=",
+          "version": "2.1.1",
+          "resolved": "https://registry.npmjs.org/string-width/-/string-width-2.1.1.tgz",
+          "integrity": "sha512-nOqH59deCq9SRHlxq1Aw85Jnt4w6KvLKqWVik6oA9ZklXLNIOlqg4F2yrT1MVaTjAqvVwdfeZ7w7aCvJD7ugkw==",
           "dev": true,
           "requires": {
-            "ansi-regex": "^2.0.0"
+            "is-fullwidth-code-point": "^2.0.0",
+            "strip-ansi": "^4.0.0"
           }
         }
       }
diff --git a/package.json b/package.json
index 223aa6c..cea782b 100644
--- a/package.json
+++ b/package.json
@@ -27,7 +27,7 @@
     "mdast-util-heading-range": "^2.1.0",
     "meow": "^4.0.0",
     "mz": "^2.7.0",
-    "opn": "^5.1.0",
+    "opn": "^6.0.0",
     "querystring": "^0.2.0",
     "remark-parse": "^4.0.0",
     "standard": "^12.0.1",