diff --git a/src/wp-includes/css/buttons.css b/src/wp-includes/css/buttons.css
index 1908dea3c68a5..b410825212d9a 100644
--- a/src/wp-includes/css/buttons.css
+++ b/src/wp-includes/css/buttons.css
@@ -59,16 +59,6 @@ TABLE OF CONTENTS:
 	box-sizing: border-box;
 }
 
-/* Remove the dotted border on :focus and the extra padding in Firefox */
-.wp-core-ui button::-moz-focus-inner,
-.wp-core-ui input[type="reset"]::-moz-focus-inner,
-.wp-core-ui input[type="button"]::-moz-focus-inner,
-.wp-core-ui input[type="submit"]::-moz-focus-inner {
-	border-width: 0;
-	border-style: none;
-	padding: 0;
-}
-
 /* Compact size - 32px, for space-constrained contexts */
 .wp-core-ui .button.button-compact,
 .wp-core-ui .button-group.button-compact .button {
diff --git a/src/wp-includes/css/editor.css b/src/wp-includes/css/editor.css
index fcc3198b6a8ac..86c9db87b3d32 100644
--- a/src/wp-includes/css/editor.css
+++ b/src/wp-includes/css/editor.css
@@ -706,13 +706,6 @@ div.mce-menu .mce-menu-item-sep,
 	box-shadow: 0 1px 0 #c3c4c7;
 }
 
-/* Remove the dotted border on :focus and the extra padding in Firefox */
-.mce-window .mce-btn::-moz-focus-inner {
-	border-width: 0;
-	border-style: none;
-	padding: 0;
-}
-
 .mce-window .mce-btn:hover,
 .mce-window .mce-btn:focus {
 	background: #f6f7f7;
diff --git a/src/wp-includes/css/jquery-ui-dialog.css b/src/wp-includes/css/jquery-ui-dialog.css
index 8bc8014808c07..602973924657b 100644
--- a/src/wp-includes/css/jquery-ui-dialog.css
+++ b/src/wp-includes/css/jquery-ui-dialog.css
@@ -232,13 +232,6 @@
 	outline: none;
 }
 
-/* Remove the dotted border on :focus and the extra padding in Firefox */
-.ui-button::-moz-focus-inner {
-	border-width: 0;
-	border-style: none;
-	padding: 0;
-}
-
 .ui-button:hover,
 .ui-button:focus {
 	background: #f6f7f7;