diff --git a/edit/codemirror-default.js b/edit/codemirror-default.js
index 6c63f299..816671ab 100644
--- a/edit/codemirror-default.js
+++ b/edit/codemirror-default.js
@@ -176,8 +176,8 @@
 
     const execAt = (rx, i) => (rx.lastIndex = i) && null || rx.exec(text);
     const at = (rx, i) => (rx.lastIndex = i) && null || rx.test(text);
-    const atWord = ch => at(/\w/uy, ch);
-    const atSpace = ch => at(/\s/uy, ch);
+    const atWord = ch => at(/\w/y, ch);
+    const atSpace = ch => at(/\s/y, ch);
 
     const atTokenEnd = styles.indexOf(ch, 1);
     ch += atTokenEnd < 0 ? 0 : sticky === 'before' && atWord(ch - 1) ? 0 : atSpace(ch + 1) ? 0 : 1;
@@ -189,19 +189,19 @@
     const isNumber = type === 'number';
     const isSpace = atSpace(ch);
     let wordChars =
-      isNumber ? /[-+\w.%]/uy :
-      isCss ? /[-\w@]/uy :
-      isSpace ? /\s/uy :
-      atWord(ch) ? /\w/uy : /[^\w\s]/uy;
+      isNumber ? /[-+\w.%]/y :
+      isCss ? /[-\w@]/y :
+      isSpace ? /\s/y :
+      atWord(ch) ? /\w/y : /[^\w\s]/y;
 
     let a = ch;
     while (a && at(wordChars, a)) a--;
-    a += !a && at(wordChars, a) || isCss && at(/[.!#@]/uy, a) ? 0 : at(wordChars, a + 1);
+    a += !a && at(wordChars, a) || isCss && at(/[.!#@]/y, a) ? 0 : at(wordChars, a + 1);
 
     let b, found;
 
     if (isNumber) {
-      b = a + execAt(/[+-]?[\d.]+(e\d+)?|$/uyi, a)[0].length;
+      b = a + execAt(/[+-]?[\d.]+(e\d+)?|$/yi, a)[0].length;
       found = b >= ch;
       if (!found) {
         a = b;
@@ -210,7 +210,7 @@
     }
 
     if (!found) {
-      wordChars = isCss ? /[-\w]*/uy : new RegExp(wordChars.source + '*', 'uy');
+      wordChars = isCss ? /[-\w]*/y : new RegExp(wordChars.source + '*', 'uy');
       b = ch + execAt(wordChars, ch)[0].length;
     }
 
@@ -226,7 +226,7 @@ CodeMirror.hint && (() => {
   const USO_VAR = 'uso-variable';
   const USO_VALID_VAR = 'variable-3 ' + USO_VAR;
   const USO_INVALID_VAR = 'error ' + USO_VAR;
-  const RX_IMPORTANT = /(i(m(p(o(r(t(a(nt?)?)?)?)?)?)?)?)?(?=\b|\W|$)/iyu;
+  const RX_IMPORTANT = /(i(m(p(o(r(t(a(nt?)?)?)?)?)?)?)?)?(?=\b|\W|$)/iy;
 
   const originalHelper = CodeMirror.hint.css || (() => {});
   CodeMirror.registerHelper('hint', 'css', function (cm) {
@@ -238,7 +238,7 @@ CodeMirror.hint && (() => {
     if (style && (style.startsWith('comment') || style.startsWith('string'))) {
       return originalHelper(cm);
     }
-    if (text[ch - 1] === '!' && /i|\W|^$/iu.test(text[ch] || '')) {
+    if (text[ch - 1] === '!' && /i|\W|^$/i.test(text[ch] || '')) {
       RX_IMPORTANT.lastIndex = ch;
       return {
         list: ['important'],
diff --git a/js/moz-parser.js b/js/moz-parser.js
index f97de26e..f5e7eb8e 100644
--- a/js/moz-parser.js
+++ b/js/moz-parser.js
@@ -34,7 +34,7 @@ function parseMozFormat({code, styleId}) {
     // move last comment before @-moz-document inside the section
     if (!lastCmt.includes('AGENT_SHEET') &&
         !lastCmt.includes('==') &&
-        !/==userstyle==/iu.test(lastCmt)) {
+        !/==userstyle==/i.test(lastCmt)) {
       if (lastCmt) {
         section.code = lastCmt + '\n';
         outerText = outerText.slice(0, -lastCmt.length);
diff --git a/vendor-overwrites/csslint/csslint.js b/vendor-overwrites/csslint/csslint.js
index cdcbc9c1..fb0a3b8e 100644
--- a/vendor-overwrites/csslint/csslint.js
+++ b/vendor-overwrites/csslint/csslint.js
@@ -112,7 +112,7 @@ class Reporter {
 //eslint-disable-next-line no-var
 var CSSLint = (() => {
 
-  const RX_EMBEDDED = /\/\*\s*csslint\s+((?:[^*]|\*(?!\/))+?)\*\//igu;
+  const RX_EMBEDDED = /\/\*\s*csslint\s+((?:[^*]|\*(?!\/))+?)\*\//ig;
   const EBMEDDED_RULE_VALUE_MAP = {
     // error
     'true':  2,
diff --git a/vendor-overwrites/csslint/parserlib.js b/vendor-overwrites/csslint/parserlib.js
index 69616c61..442d8faa 100644
--- a/vendor-overwrites/csslint/parserlib.js
+++ b/vendor-overwrites/csslint/parserlib.js
@@ -3354,15 +3354,15 @@ self.parserlib = (() => {
     }
 
     readUnquotedURL(first) {
-      return this.readChunksWithEscape(first, /[-!#$%&*-[\]-~\u00A0-\uFFFF]+/yu);
+      return this.readChunksWithEscape(first, /[-!#$%&*-[\]-~\u00A0-\uFFFF]+/y);
     }
 
     readName(first) {
-      return this.readChunksWithEscape(first, /[-_\da-zA-Z\u00A0-\uFFFF]+/yu);
+      return this.readChunksWithEscape(first, /[-_\da-zA-Z\u00A0-\uFFFF]+/y);
     }
 
     readEscape() {
-      const cp = this._reader.readMatch(/[0-9a-f]{1,6}\b\s*/iyu);
+      const cp = this._reader.readMatch(/[0-9a-f]{1,6}\b\s*/iy);
       return cp ? String.fromCodePoint(parseInt(cp, 16)) : this._reader.read();
     }
 
@@ -3388,7 +3388,7 @@ self.parserlib = (() => {
     readComment(first) {
       return first +
              this._reader.readCount(2 - first.length) +
-             this._reader.readMatch(/([^*]|\*(?!\/))*(\*\/|$)/yu);
+             this._reader.readMatch(/([^*]|\*(?!\/))*(\*\/|$)/y);
     }
   }