diff --git a/core/constants.js b/core/constants.js
index 1d07e9ac..756a5950 100644
--- a/core/constants.js
+++ b/core/constants.js
@@ -90,5 +90,6 @@ const Whitelist = {
 };
 
 const BrowserType = {
-    'CHROMIUM': chrome.runtime.getURL("/").startsWith("chrome-extension")
+    'CHROMIUM': chrome.runtime.getURL("/").startsWith("chrome-extension"),
+    'FIREFOX': chrome.runtime.getURL("/").startsWith("moz-extension")
 }
diff --git a/core/manipulate-dom.js b/core/manipulate-dom.js
new file mode 100644
index 00000000..c41e5018
--- /dev/null
+++ b/core/manipulate-dom.js
@@ -0,0 +1,97 @@
+/**
+ * Remove integrity checks from embedded CSS and JavaScript files
+ * Belongs to LocalCDN.
+ *
+ * @author      nobody42
+ * @since       2020-02-27
+ *
+ * @license     MPL 2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+'use strict';
+
+
+/**
+ * Manipulate DOM
+ */
+
+var manipulateDOM = {};
+
+
+/**
+ * Private Methods
+ */
+
+manipulateDOM._removeCrossOriginAndIntegrityAttr = function (details) {
+
+    // by Jaap (https://gitlab.com/Jaaap)
+    // https://gitlab.com/nobody42/localcdn/-/issues/66
+    let header = details.responseHeaders.find(h => h.name.toLowerCase() === 'content-type');
+
+    if (header && BrowserType.FIREFOX) {
+
+        let mimeType, charset, initiatorDomain, isWhitelisted;
+
+        mimeType = header.value.replace(/;.*/, '').toLowerCase();
+        charset = /charset\s*=/.test(header.value) ? header.value.replace(/^.*?charset\s*=\s*/, '') : 'UTF-8';
+        initiatorDomain = helpers.extractDomainFromUrl(details.url, true) || Address.EXAMPLE;
+        isWhitelisted = stateManager._domainIsWhitelisted(initiatorDomain);
+
+        if (!isWhitelisted && mimeType === 'text/html') {
+
+            header.value = 'text/html; charset=UTF-8';
+            let decoder = new TextDecoder(charset);
+            let encoder = new TextEncoder();
+            let filter = browser.webRequest.filterResponseData(details.requestId);
+
+            //Note that this will not work if the '<script crossorigin="anonymous" src="dfgsfgd.com">' string is divided into two chunks, but we want to flush this data asap.
+            filter.ondata = evt => {
+                //remove crossorigin and integrity attributes
+                let str = decoder.decode(evt.data, {stream: true}).replace(/<(link|script)[^>]+>/ig, m => {
+                        if (cdnDomainsRE.test(m))
+                            return m.replace(/\s+(integrity|crossorigin)(="[^"]*"|='[^']*'|=[^"'`=\s]+|)/ig, '');
+                        return m;
+                    });
+                filter.write(encoder.encode(str));
+            }
+
+            filter.onstop = evt => {
+                let str = decoder.decode(); //end-of-stream
+                filter.write(encoder.encode(str));
+                filter.close();
+            }
+        }
+
+    } else if(BrowserType.CHROMIUM) {
+
+        // Chromium browsers do not support webRequest.filterResponseData
+        // https://bugs.chromium.org/p/chromium/issues/detail?id=487422
+        console.warn('[ LocalCDN ] browser.webRequest.filterResponseData not supported by your browser.');
+
+    }
+    return {responseHeaders: details.responseHeaders};
+
+};
+
+
+/**
+ * Initializations
+ */
+
+ let whitelistedDomains = {};
+ let cdnDomainsRE = new RegExp('//(' + Object.keys(mappings).map(m => m.replace(/\W/g, '\\$&')).join('|') + ')/');
+
+
+/**
+* Event Handlers
+*/
+
+chrome.webRequest.onHeadersReceived.addListener(
+    manipulateDOM._removeCrossOriginAndIntegrityAttr,
+    {'types': [WebRequestType.MAIN_FRAME], 'urls': [Address.ANY]},
+	[WebRequest.BLOCKING, WebRequest.RESPONSE_HEADERS]
+);
diff --git a/core/state-manager.js b/core/state-manager.js
index 500674ac..f66e7e04 100644
--- a/core/state-manager.js
+++ b/core/state-manager.js
@@ -281,53 +281,6 @@ stateManager._setIconDisabled = function (tabIdentifier) {
     });
 };
 
-stateManager._getContentType = function (headers) {
-
-    // by Jaap (https://gitlab.com/Jaaap)
-    for (let header of headers) {
-        if (header.name.toLowerCase() === "content-type") { //"text/html; charset=UTF-8"
-            return {
-                mimeType: header.value.replace(/;.*/, '').toLowerCase(),
-                charset: /charset\s*=/.test(header.value) ? header.value.replace(/^.*?charset\s*=\s*/, '') : 'UTF-8'
-            };
-        }
-    }
-    return { mimeType: '', charset: '' };
-};
-
-stateManager._removeCrossoriginAndIntegrityAttr = function (details) {
-
-    // by Jaap (https://gitlab.com/Jaaap)
-    let { mimeType, charset } = stateManager._getContentType(details.responseHeaders);
-
-    let initiatorDomain = helpers.extractDomainFromUrl(details.url, true) || Address.EXAMPLE;
-    let isWhitelisted = requestAnalyzer.whitelistedDomains[initiatorDomain];
-    let cdnDomainsRE = new RegExp("//(" + Object.keys(mappings).map(m => m.replace(/\W/g, '\\$&')).join('|') + ")/");
-
-    if (!isWhitelisted && mimeType === "text/html") {
-        let decoder = new TextDecoder(charset);
-        let encoder = new TextEncoder();
-
-        let filter = browser.webRequest.filterResponseData(details.requestId);
-
-        //Note that this will not work if the '<script crossorigin="anonymous" src="dfgsfgd.com">' string is divided into two chunks, but we want to flush this data asap.
-        filter.ondata = evt => {
-            //remove crossorigin and integrity attributes
-            let str = decoder.decode(evt.data, {stream: true}).replace(/<(link|script)[^>]+>/ig, m => {
-                if (cdnDomainsRE.test(m))
-                    return m.replace(/\s+(integrity|crossorigin)(="[^"]*"|='[^']*'|=[^"'`=\s]+|)/ig, "");
-                return m;
-            });
-            filter.write(encoder.encode(str));
-        }
-
-        filter.onstop = evt => {
-            let str = decoder.decode(); // end-of-stream
-            filter.write(encoder.encode(str));
-            filter.close();
-        }
-    }
-};
 
 /**
  * Initializations
@@ -374,12 +327,6 @@ chrome.storage.local.get(Setting.SHOW_ICON_BADGE, function (items) {
 chrome.tabs.onCreated.addListener(stateManager._createTab);
 chrome.tabs.onRemoved.addListener(stateManager._removeTab);
 
-chrome.webRequest.onHeadersReceived.addListener(function (response) {
-
-        stateManager._removeCrossoriginAndIntegrityAttr(response)
-
-}, {'types': [WebRequestType.MAIN_FRAME], 'urls': [Address.ANY]}, [WebRequest.BLOCKING, WebRequest.RESPONSE_HEADERS]);
-
 chrome.webRequest.onBeforeRequest.addListener(function (requestDetails) {
 
     if (requestDetails.tabId !== -1 && stateManager.tabs[requestDetails.tabId]) {
diff --git a/pages/background/background.html b/pages/background/background.html
index 2934084b..9434b515 100644
--- a/pages/background/background.html
+++ b/pages/background/background.html
@@ -25,6 +25,7 @@
         <script src="../../core/file-guard.js"></script>
         <script src="../../core/messenger.js"></script>
         <script src="../../core/interceptor.js"></script>
+        <script src="../../core/manipulate-dom.js"></script>
         <script src="../../core/main.js"></script>
 
     </body>
diff --git a/pages/updates/updates.html b/pages/updates/updates.html
index 3e3d08af..81bd4a32 100644
--- a/pages/updates/updates.html
+++ b/pages/updates/updates.html
@@ -29,6 +29,7 @@
                             <li>Added jQuery-csv v1.0.9, jQuery Ajax AutoComplete (Devbridge) v1.4.10 and Popper.js v1.16.1 (Fixed <a href="https://gitlab.com/nobody42/localcdn/-/issues/68">#68</a>)</li>
                             <li>Font Awesome injections in Chromium deactivated (Fixed <a href="https://gitlab.com/nobody42/localcdn/-/issues/67">#67</a>)</li>
                             <li>French translation updated</li>
+                            <li>Error in encoding fixed (<a href="https://gitlab.com/nobody42/localcdn/-/issues/66#note_334647377">#66 comment: 334647377</a>)</li>
                         </ul>
                     <div class="topic-label">
                         Please update your uBlock/uMatrix rules