diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab35a7d0..5d589e87 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 # Changelog
 
+- Add HTML escaping for some titles, labels and metada that was missing.
+
 ## [4.27.1](https://github.com/mmistakes/minimal-mistakes/releases/tag/4.27.1)
 
 ### Enhancements
diff --git a/_includes/footer.html b/_includes/footer.html
index 2b2b7ee1..cde75d2f 100644
--- a/_includes/footer.html
+++ b/_includes/footer.html
@@ -7,7 +7,7 @@
     {% if site.footer.links %}
       {% for link in site.footer.links %}
         {% if link.label and link.url %}
-          <li><a href="{{ link.url }}" rel="nofollow noopener noreferrer"><i class="{{ link.icon | default: 'fas fa-link' }}" aria-hidden="true"></i> {{ link.label }}</a></li>
+          <li><a href="{{ link.url }}" rel="nofollow noopener noreferrer"><i class="{{ link.icon | default: 'fas fa-link' }}" aria-hidden="true"></i> {{ link.label | escape_once | strip }}</a></li>
         {% endif %}
       {% endfor %}
     {% endif %}
@@ -18,4 +18,4 @@
   </ul>
 </div>
 
-<div class="page__footer-copyright">&copy; {{ site.time | date: '%Y' }} <a href="{{ site.copyright_url | default: site.url }}">{{ site.copyright | default: site.title }}</a>. {{ site.data.ui-text[site.locale].powered_by | default: "Powered by" }} <a href="https://jekyllrb.com" rel="nofollow">Jekyll</a> &amp; <a href="https://mademistakes.com/work/jekyll-themes/minimal-mistakes/" rel="nofollow">Minimal Mistakes</a>.</div>
+<div class="page__footer-copyright">&copy; {{ site.time | date: '%Y' }} <a href="{{ site.copyright_url | default: site.url }}">{{ site.copyright | default: site.title | escape_once | strip }}</a>. {{ site.data.ui-text[site.locale].powered_by | default: "Powered by" }} <a href="https://jekyllrb.com" rel="nofollow">Jekyll</a> &amp; <a href="https://mademistakes.com/work/jekyll-themes/minimal-mistakes/" rel="nofollow">Minimal Mistakes</a>.</div>
diff --git a/_includes/masthead.html b/_includes/masthead.html
index f919fb77..c97b2aa3 100644
--- a/_includes/masthead.html
+++ b/_includes/masthead.html
@@ -8,8 +8,8 @@
           <a class="site-logo" href="{{ '/' | relative_url }}"><img src="{{ logo_path | relative_url }}" alt="{{ site.masthead_title | default: site.title }}"></a>
         {% endunless %}
         <a class="site-title" href="{{ '/' | relative_url }}">
-          {{ site.masthead_title | default: site.title }}
-          {% if site.subtitle %}<span class="site-subtitle">{{ site.subtitle }}</span>{% endif %}
+          {{ site.masthead_title | default: site.title | escape_once | strip }}
+          {% if site.subtitle %}<span class="site-subtitle">{{ site.subtitle | escape_once | strip }}</span>{% endif %}
         </a>
         <ul class="visible-links">
           {%- for link in site.data.navigation.main -%}
diff --git a/_includes/seo.html b/_includes/seo.html
index e500c6f3..1e04a261 100644
--- a/_includes/seo.html
+++ b/_includes/seo.html
@@ -39,15 +39,15 @@
 <meta name="description" content="{{ seo_description }}">
 
 {% if author.name %}
-  <meta name="author" content="{{ author.name | default: author }}">
+  <meta name="author" content="{{ author.name | default: author | escape_once | strip }}">
   {% if og_type == "article" %}
-  <meta property="article:author" content="{{ author.name | default: author }}">
+  <meta property="article:author" content="{{ author.name | default: author | escape_once | strip }}">
   {% endif %}
 {% endif %}
 
 <meta property="og:type" content="{{ og_type }}">
 <meta property="og:locale" content="{{ site.locale | replace: "-", "_" | default: "en_US" }}">
-<meta property="og:site_name" content="{{ site.title }}">
+<meta property="og:site_name" content="{{ site.title | escape_once | strip }}">
 <meta property="og:title" content="{{ page_title }}">
 <meta property="og:url" content="{{ canonical_url }}">