4 files changed, 14 insertions, 4 deletions
diff --git a/src/ui/options.css b/src/ui/options.css
index f7db24b..9230eb1 100644
--- a/src/ui/options.css
+++ b/src/ui/options.css
@@ -185,3 +185,11 @@ input[type="file"] {
   border-radius: .2em .2em 0 0;
   padding: .2em .4em;
 }
+
+#xss-opt-group {
+  display: none;
+}
+
+.mozwebext #xss-opt-group {
+  display: block;
+}
diff --git a/src/ui/options.html b/src/ui/options.html
index 4d44d75..5198795 100644
--- a/src/ui/options.html
+++ b/src/ui/options.html
@@ -101,7 +101,7 @@
 
 <h3 class="flextabs__tab"><button class="flextabs__toggle">__MSG_SectionAdvanced__</button></h3>
 <div class="flextabs__content">
-  <div class="opt-group">
+  <div class="opt-group" id="xss-opt-group">
   <span id="xss-opts">
     <input type="checkbox" id="opt-xss"><label for="opt-xss" id="lbl-xss">__MSG_OptFilterXGet__</label>
   <span id="xssFaq">(<a href="https://noscript.net/faq#xss" title="https://noscript.net/faq#xss">__MSG_XssFaq__</a>)</span>
diff --git a/src/ui/options.js b/src/ui/options.js
index 31cf5c3..a3f7fe8 100644
--- a/src/ui/options.js
+++ b/src/ui/options.js
@@ -8,9 +8,9 @@
   let version = browser.runtime.getManifest().version;
   document.querySelector("#version").textContent = _("Version", version);
   // simple general options
-  
+
   let opt = UI.wireOption;
-  
+
   opt("global", o => {
     if (o) {
       policy.enforced = !o.checked;
@@ -96,7 +96,7 @@
     }
     let button = document.querySelector("#btn-delete-xss-choices");
     let choices = UI.xssUserChoices;
-    button.disabled = Object.keys(choices).length === 0;
+    button.disabled = !choices || Object.keys(choices).length === 0;
     button.onclick = () => {
       UI.updateSettings({
         xssUserChoices: {}
diff --git a/src/xss/XSS.js b/src/xss/XSS.js
index f95ea04..7851e98 100644
--- a/src/xss/XSS.js
+++ b/src/xss/XSS.js
@@ -113,6 +113,8 @@ var XSS = (() => {
 
   return {
     async start() {
+      if (!UA.isMozilla) return; // async webRequest is supported on Mozilla only
+
       let {onBeforeRequest} = browser.webRequest;
       if (onBeforeRequest.hasListener(requestListener)) return;