diff --git a/introduction/welcome/changelog.xml b/introduction/welcome/changelog.xml
index d048011c1b..19cb3aaef3 100644
--- a/introduction/welcome/changelog.xml
+++ b/introduction/welcome/changelog.xml
@@ -45,6 +45,11 @@
           <para>[bdubbs] - Update to libxfce4ui-4.18.1. Fixes
           <ulink url="&blfs-ticket-root;17477">#17477</ulink>.</para>
         </listitem>
+        <listitem>
+          <para>[ken] - Update to qtwebengine-5.15.12 (Security fix) with
+          qmake switch to let ffmpeg decode proprietary codecs. Fixes
+          <ulink url="&blfs-ticket-root;17478">#17478</ulink>.</para>
+        </listitem>
       </itemizedlist>
     </listitem>
 
diff --git a/packages.ent b/packages.ent
index bc8b29d31a..ea45a51b01 100644
--- a/packages.ent
+++ b/packages.ent
@@ -722,7 +722,7 @@ to avoid building libxml2 twice, which is slow with all deps -->
 <!ENTITY pango-version                "&pango-minor;.12">
 <!ENTITY pangomm-version              "2.46.3">
 <!ENTITY qt5-version                  "5.15.8">
-<!ENTITY qtwebengine-version          "5.15.11">
+<!ENTITY qtwebengine-version          "5.15.12">
 <!ENTITY startup-notification-version "0.12">
 <!ENTITY tepl-version                 "6.4.0">
 <!ENTITY webkitgtk-version            "2.38.3">    <!-- Even minors only -->
diff --git a/x/lib/qtwebengine.xml b/x/lib/qtwebengine.xml
index e2b0c083ac..86ea8353e1 100644
--- a/x/lib/qtwebengine.xml
+++ b/x/lib/qtwebengine.xml
@@ -10,10 +10,10 @@
      URL for a prepared git version -->
   <!ENTITY qtwebengine-download-http "&sources-anduin-http;/qtwebengine/qtwebengine-&qtwebengine-version;.tar.xz">
   <!ENTITY qtwebengine-download-ftp  " ">
-  <!ENTITY qtwebengine-md5sum        "1302667c7e8a045fb0cc776f7e3627ad">
-  <!ENTITY qtwebengine-size          "306 MB">
+  <!ENTITY qtwebengine-md5sum        "a874390e7987ae5613f4650aab5681e8">
+  <!ENTITY qtwebengine-size          "307 MB">
   <!ENTITY qtwebengine-buildsize     "5.1 GB (152 MB installed)">
-  <!ENTITY qtwebengine-time          "103 SBU (typical, Using parallelism=4)">
+  <!ENTITY qtwebengine-time          "79 SBU (on a fast machine, Using parallelism=4)">
 ]>
 
 <sect1 id="qtwebengine" xreflabel="qtwebengine-&qtwebengine-version;">
@@ -432,7 +432,7 @@ fi</userinput></screen>-->
 
 <screen><userinput>mkdir build &amp;&amp;
 cd    build &amp;&amp;
-qmake .. -- -system-ffmpeg -webengine-icu &amp;&amp;
+qmake .. -- -system-ffmpeg -proprietary-codecs -webengine-icu &amp;&amp;
 make</userinput></screen>
 
 <!--
@@ -488,13 +488,14 @@ make</userinput></screen>
     </para>
 
     <para>
-      <command>-- -system-ffmpeg -webengine-icu</command>: If any options are
-      passed to qmake they must come after '--' which must follow '..' that points
-      to the main directory. The options here cause it to use system ffmpeg and
-      system icu.  If built as part of full Qt5, the system icu is automatically
-      used (only) by Qt5Core if it is available, but unless this option is used
-      webengine will always use its shipped copy of icu, adding time and space
-      to the build.
+      <command>-- -system-ffmpeg -proprietary-codecs -webengine-icu</command>: If
+      any options are passed to qmake they must come after '--' which must follow
+      '..' that points to the main directory. The options here cause it to use
+      system ffmpeg and  system icu. The '-proprietary-codecs' option allows
+      ffmpeg to decode H264 and H265 codecs.  If built as part of full Qt5, the
+      system icu is automatically used (only) by Qt5Core if it is available, but
+      unless this option is used webengine will always use its shipped copy of icu,
+      adding time and space to the build.
     </para>
 
     <para>