[XSS] Restored compatibility with Gecko 77 and below.

src/nscl

@@ -1 +1 @@
-Subproject commit b0b355de528b11b8ae641b429f3442fe19bbff67
+Subproject commit 2bf555fca3aa803fa72fd43ef94403aefb1254a5

src/xss/InjectionChecker.js

@@ -49,7 +49,7 @@ XSS.InjectionChecker = (async () => {
     "|\\b(?:" + IC_WINDOW_OPENER_PATTERN + ")\\b[^]+\\b(?:" + IC_EVENT_PATTERN + ")[^]*=";
 
   function InjectionChecker() {
-    this.timing = new Timing();
+    this.timing = new Timing(20);
     this.reset();
   }
   InjectionChecker.prototype = {
@@ -492,8 +492,44 @@ XSS.InjectionChecker = (async () => {
       return ret;
     },
 
-    // see https://mathiasbynens.be/notes/javascript-identifiers-es6#acceptable-unicode-symbols
-    invalidCharsRx: /^[^"'`/<>]*[^$_\p{ID_Start}\p{ID_Continue}\u200c\u200d]/u,
+    _createInvalidRanges: function() {
+      function x(n) {
+        return '\\u' + ("0000" + n.toString(16)).slice(-4);
+      }
+
+      let chunks = [];
+      let first = -1;
+      let last = -1;
+      let cur = 0x7e;
+      let close = () => { if (last != first) chunks.push(`-${x(last)}`); }
+      while (cur++ < 0xffff) {
+        try {
+           Function(`let _${String.fromCharCode(cur)}_`);
+        } catch (e) {
+          if (!/illegal char/.test(e.message)) continue;
+          if (first == -1) {
+            first = last = cur;
+            chunks.push(x(cur));
+            continue;
+          }
+          if (cur - last == 1) {
+            last = cur;
+            continue;
+          }
+          close();
+          chunks.push(x(cur));
+          last = first = cur;
+        }
+      }
+      close();
+      return chunks.join('');
+    },
+
+    get invalidCharsRx() {
+      let value = new RegExp("^[^\"'`/<>]*[" + this._createInvalidRanges() + "]");
+      Object.defineProperty(Object.getPrototypeOf(this), 'invalidCharsRx', {value});
+      return value;
+    },
 
     async checkJSBreak(s) {
       // Direct script injection breaking JS string literals or comments