diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index a24c66bdee1..dcef8ea97fc 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -1,3 +1,8 @@
+Drupal 7.80, 2021-04-20
+-----------------------
+- Fixed security issues:
+   - SA-CORE-2021-002
+
 Drupal 7.79, 2021-04-07
 -----------------------
 - Initial support for PHP 8
diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index 0955260211c..72c92911d2d 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -8,7 +8,7 @@
 /**
  * The current system version.
  */
-define('VERSION', '7.79');
+define('VERSION', '7.80');
 
 /**
  * Core API compatibility.
diff --git a/includes/common.inc b/includes/common.inc
index 88dc7a8bcd4..a19a5eaacc6 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -1618,7 +1618,13 @@ function _filter_xss_attributes($attr) {
         // Attribute name, href for instance.
         if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) {
           $attrname = strtolower($match[1]);
-          $skip = ($attrname == 'style' || substr($attrname, 0, 2) == 'on');
+          $skip = (
+            $attrname == 'style' ||
+            substr($attrname, 0, 2) == 'on' ||
+            substr($attrname, 0, 1) == '-' ||
+            // Ignore long attributes to avoid unnecessary processing overhead.
+            strlen($attrname) > 96
+          );
           $working = $mode = 1;
           $attr = preg_replace('/^[-a-zA-Z]+/', '', $attr);
         }
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 713662df69f..3e88c383430 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -323,7 +323,7 @@
  *
  * To see what PHP settings are possible, including whether they can be set at
  * runtime (by using ini_set()), read the PHP documentation:
- * http://www.php.net/manual/en/ini.list.php
+ * http://www.php.net/manual/ini.list.php
  * See drupal_environment_initialize() in includes/bootstrap.inc for required
  * runtime settings and the .htaccess file for non-runtime settings. Settings
  * defined there should not be duplicated here so as to avoid conflict issues.
@@ -359,7 +359,7 @@
  * output filter may not have sufficient memory to process it.  If you
  * experience this issue, you may wish to uncomment the following two lines
  * and increase the limits of these variables.  For more information, see
- * http://php.net/manual/en/pcre.configuration.php.
+ * http://php.net/manual/pcre.configuration.php.
  */
 # ini_set('pcre.backtrack_limit', 200000);
 # ini_set('pcre.recursion_limit', 200000);
@@ -634,15 +634,6 @@
  */
 # $conf['allow_authorize_operations'] = FALSE;
 
-/**
- * Smart start:
- *
- * If you would prefer to be redirected to the installation system when a
- * valid settings.php file is present but no tables are installed, remove
- * the leading hash sign below.
- */
-# $conf['pressflow_smart_start'] = TRUE;
-
 /**
  * Theme debugging:
  *
@@ -711,6 +702,15 @@
  */
 # $conf['variable_initialize_wait_for_lock'] = FALSE;
 
+/**
+ * Opt in to field_sql_storage_field_storage_write() optimization.
+ *
+ * To reduce unnecessary writes field_sql_storage_field_storage_write() can skip
+ * fields where values have apparently not changed. To opt in to this
+ * optimization, set this variable to TRUE.
+ */
+$conf['field_sql_storage_skip_writing_unchanged_fields'] = TRUE;
+
 /**
  * Use site name as display-name in outgoing mail.
  *
@@ -725,3 +725,23 @@
  * @see drupal_mail()
  */
 $conf['mail_display_name_site_name'] = TRUE;
+
+/**
+ * SameSite cookie attribute.
+ *
+ * This variable can be used to set a value for the SameSite cookie attribute.
+ *
+ * Versions of PHP before 7.3 have no native support for the SameSite attribute
+ * so it is emulated.
+ *
+ * The session.cookie-samesite setting in PHP 7.3 and later will be overridden
+ * by this variable for Drupal session cookies, and any other cookies managed
+ * with drupal_setcookie().
+ *
+ * Setting this variable to FALSE disables the SameSite attribute on cookies.
+ *
+ * @see drupal_setcookie()
+ * @see drupal_session_start()
+ * @see https://www.php.net/manual/en/session.configuration.php#ini.session.cookie-samesite
+ */
+#$conf['samesite_cookie_value'] = 'None';