diff --git a/core/manipulate-dom.js b/core/manipulate-dom.js
index bf765b5a..39a5c6db 100644
--- a/core/manipulate-dom.js
+++ b/core/manipulate-dom.js
@@ -97,7 +97,10 @@ manipulateDOM._removeCrossOriginAndIntegrityAttr = function (details) {
                             if (EncodingTypes[charsetMatch[1].toLowerCase()] !== undefined) {
                                 charset = charsetMatch[1];
                             } else {
-                                charset = 'UTF-8';
+                                // If charset is unclear, then use ASCII by default.
+                                // Other charsets are mostly tagged in the header or HTML source code.
+                                // https://codeberg.org/nobody/LocalCDN/issues/567
+                                charset = 'ASCII';
                             }
                         }
                         decoder = new TextDecoder(charset);
diff --git a/pages/updates/updates.html b/pages/updates/updates.html
index 3f036782..5336fadb 100644
--- a/pages/updates/updates.html
+++ b/pages/updates/updates.html
@@ -62,6 +62,7 @@
                         <li>Mapping: jquery-mobile -> ajax.googleapis.com (<a href="https://codeberg.org/nobody/LocalCDN/issues/564">#564</a>)</li>
                         <li>Updated: highlight.js v11.0.1 -> v11.1.0 (<a href="https://codeberg.org/nobody/LocalCDN/issues/565">#565</a>)</li>
                         <li>Updated: socket.io v4.1.2 -> v4.1.3 (<a href="https://codeberg.org/nobody/LocalCDN/issues/566">#566</a>)</li>
+                        <li>Fixed: Default cahrset of HTML filter (<a href="https://codeberg.org/nobody/LocalCDN/issues/567">#567</a>)</li>
                         <li><strong>Includes also the following changes, because the release of this version took a long time caused by a broken validation server of Mozilla (<a href="https://codeberg.org/nobody/LocalCDN/issues/490">More information</a>).</strong>
                             <ul>
                                 <li>Ruleset generator for NoScript (<a href="https://codeberg.org/nobody/LocalCDN/issues/489">#489</a>)</li>