diff --git a/src/wp-includes/cache.php b/src/wp-includes/cache.php
index ddfd6e2acd..52e58b4733 100644
--- a/src/wp-includes/cache.php
+++ b/src/wp-includes/cache.php
@@ -668,7 +668,7 @@ class WP_Object_Cache {
 		echo "</p>";
 		echo '<ul>';
 		foreach ($this->cache as $group => $cache) {
-			echo "<li><strong>Group:</strong> $group - ( " . number_format( strlen( serialize( $cache ) ) / KB_IN_BYTES, 2 ) . 'k )</li>';
+			echo '<li><strong>Group:</strong> ' . esc_html( $group ) . ' - ( ' . number_format( strlen( serialize( $cache ) ) / KB_IN_BYTES, 2 ) . 'k )</li>';
 		}
 		echo '</ul>';
 	}
diff --git a/src/wp-includes/class-wp-customize-manager.php b/src/wp-includes/class-wp-customize-manager.php
index 1a5360d551..1787739186 100644
--- a/src/wp-includes/class-wp-customize-manager.php
+++ b/src/wp-includes/class-wp-customize-manager.php
@@ -2859,13 +2859,12 @@ final class WP_Customize_Manager {
 		$this->store_changeset_revision = $allow_revision;
 		add_filter( 'wp_save_post_revision_post_has_changed', array( $this, '_filter_revision_post_has_changed' ), 5, 3 );
 
-		// Update the changeset post. The publish_customize_changeset action will cause the settings in the changeset to be saved via WP_Customize_Setting::save().
-		$has_kses = ( false !== has_filter( 'content_save_pre', 'wp_filter_post_kses' ) );
-		if ( $has_kses ) {
-			kses_remove_filters(); // Prevent KSES from corrupting JSON in post_content.
-		}
-
-		// Note that updating a post with publish status will trigger WP_Customize_Manager::publish_changeset_values().
+		/*
+		 * Update the changeset post. The publish_customize_changeset action will cause the settings in the
+		 * changeset to be saved via WP_Customize_Setting::save(). Updating a post with publish status will
+		 * trigger WP_Customize_Manager::publish_changeset_values().
+		 */
+		add_filter( 'wp_insert_post_data', array( $this, 'preserve_insert_changeset_post_content' ), 5, 3 );
 		if ( $changeset_post_id ) {
 			if ( $args['autosave'] && 'auto-draft' !== get_post_status( $changeset_post_id ) ) {
 				// See _wp_translate_postdata() for why this is required as it will use the edit_post meta capability.
@@ -2892,9 +2891,9 @@ final class WP_Customize_Manager {
 				$this->_changeset_post_id = $r; // Update cached post ID for the loaded changeset.
 			}
 		}
-		if ( $has_kses ) {
-			kses_init_filters();
-		}
+
+		remove_filter( 'wp_insert_post_data', array( $this, 'preserve_insert_changeset_post_content' ), 5 );
+
 		$this->_changeset_data = null; // Reset so WP_Customize_Manager::changeset_data() will re-populate with updated contents.
 
 		remove_filter( 'wp_save_post_revision_post_has_changed', array( $this, '_filter_revision_post_has_changed' ) );
@@ -2911,6 +2910,51 @@ final class WP_Customize_Manager {
 		return $response;
 	}
 
+	/**
+	 * Preserve the initial JSON post_content passed to save into the post.
+	 *
+	 * This is needed to prevent KSES and other {@see 'content_save_pre'} filters
+	 * from corrupting JSON data.
+	 *
+	 * Note that WP_Customize_Manager::validate_setting_values() have already
+	 * run on the setting values being serialized as JSON into the post content
+	 * so it is pre-sanitized.
+	 *
+	 * Also, the sanitization logic is re-run through the respective
+	 * WP_Customize_Setting::sanitize() method when being read out of the
+	 * changeset, via WP_Customize_Manager::post_value(), and this sanitized
+	 * value will also be sent into WP_Customize_Setting::update() for
+	 * persisting to the DB.
+	 *
+	 * Multiple users can collaborate on a single changeset, where one user may
+	 * have the unfiltered_html capability but another may not. A user with
+	 * unfiltered_html may add a script tag to some field which needs to be kept
+	 * intact even when another user updates the changeset to modify another field
+	 * when they do not have unfiltered_html.
+	 *
+	 * @since 5.4.1
+	 *
+	 * @param array $data                An array of slashed and processed post data.
+	 * @param array $postarr             An array of sanitized (and slashed) but otherwise unmodified post data.
+	 * @param array $unsanitized_postarr An array of slashed yet *unsanitized* and unprocessed post data as originally passed to wp_insert_post().
+	 * @return array Filtered post data.
+	 */
+	public function preserve_insert_changeset_post_content( $data, $postarr, $unsanitized_postarr ) {
+		if (
+			isset( $data['post_type'] ) &&
+			isset( $unsanitized_postarr['post_content'] ) &&
+			'customize_changeset' === $data['post_type'] ||
+			(
+				'revision' === $data['post_type'] &&
+				! empty( $data['post_parent'] ) &&
+				'customize_changeset' === get_post_type( $data['post_parent'] )
+			)
+		) {
+			$data['post_content'] = $unsanitized_postarr['post_content'];
+		}
+		return $data;
+	}
+
 	/**
 	 * Trash or delete a changeset post.
 	 *
diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index 4be11581c4..ec88da43c6 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -759,10 +759,6 @@ class WP_Query {
 			$this->is_single = true;
 		} elseif ( $qv['p'] ) {
 			$this->is_single = true;
-		} elseif ( ('' !== $qv['hour']) && ('' !== $qv['minute']) &&('' !== $qv['second']) && ('' != $qv['year']) && ('' != $qv['monthnum']) && ('' != $qv['day']) ) {
-			// If year, month, day, hour, minute, and second are set, a single
-			// post is being queried.
-			$this->is_single = true;
 		} elseif ( '' != $qv['pagename'] || !empty($qv['page_id']) ) {
 			$this->is_page = true;
 			$this->is_single = false;
diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index f1851d2994..5ed80f0c80 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -1776,6 +1776,24 @@ function remove_accents( $string ) {
 function sanitize_file_name( $filename ) {
 	$filename_raw = $filename;
 	$special_chars = array("?", "[", "]", "/", "\\", "=", "<", ">", ":", ";", ",", "'", "\"", "&", "$", "#", "*", "(", ")", "|", "~", "`", "!", "{", "}", "%", "+", chr(0));
+
+	// Check for support for utf8 in the installed PCRE library once and store the result in a static.
+	static $utf8_pcre = null;
+	if ( ! isset( $utf8_pcre ) ) {
+		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
+		$utf8_pcre = @preg_match( '/^./u', 'a' );
+	}
+
+	if ( ! seems_utf8( $filename ) ) {
+		$_ext     = pathinfo( $filename, PATHINFO_EXTENSION );
+		$_name    = pathinfo( $filename, PATHINFO_FILENAME );
+		$filename = sanitize_title_with_dashes( $_name ) . '.' . $_ext;
+	}
+
+	if ( $utf8_pcre ) {
+		$filename = preg_replace( "#\x{00a0}#siu", ' ', $filename );
+	}
+
 	/**
 	 * Filters the list of characters to remove from a filename.
 	 *
@@ -1785,7 +1803,6 @@ function sanitize_file_name( $filename ) {
 	 * @param string $filename_raw  Filename as it was passed into sanitize_file_name().
 	 */
 	$special_chars = apply_filters( 'sanitize_file_name_chars', $special_chars, $filename_raw );
-	$filename = preg_replace( "#\x{00a0}#siu", ' ', $filename );
 	$filename = str_replace( $special_chars, '', $filename );
 	$filename = str_replace( array( '%20', '+' ), '-', $filename );
 	$filename = preg_replace( '/[\r\n\t -]+/', '-', $filename );
diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index a199ee4c83..4cc16dbb04 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -3136,6 +3136,9 @@ function wp_get_recent_posts( $args = array(), $output = ARRAY_A ) {
 function wp_insert_post( $postarr, $wp_error = false ) {
 	global $wpdb;
 
+	// Capture original pre-sanitized array for passing into filters.
+	$unsanitized_postarr = $postarr;
+
 	$user_id = get_current_user_id();
 
 	$defaults = array(
@@ -3432,21 +3435,27 @@ function wp_insert_post( $postarr, $wp_error = false ) {
 		 * Filters attachment post data before it is updated in or added to the database.
 		 *
 		 * @since 3.9.0
+		 * @since 5.4.1 `$unsanitized_postarr` argument added.
 		 *
-		 * @param array $data    An array of sanitized attachment post data.
-		 * @param array $postarr An array of unsanitized attachment post data.
+		 * @param array $data                An array of slashed, sanitized, and processed attachment post data.
+		 * @param array $postarr             An array of slashed and sanitized attachment post data, but not processed.
+		 * @param array $unsanitized_postarr An array of slashed yet *unsanitized* and unprocessed attachment post data
+		 *                                   as originally passed to wp_insert_post().
 		 */
-		$data = apply_filters( 'wp_insert_attachment_data', $data, $postarr );
+		$data = apply_filters( 'wp_insert_attachment_data', $data, $postarr, $unsanitized_postarr );
 	} else {
 		/**
 		 * Filters slashed post data just before it is inserted into the database.
 		 *
 		 * @since 2.7.0
+		 * @since 5.4.1 `$unsanitized_postarr` argument added.
 		 *
-		 * @param array $data    An array of slashed post data.
-		 * @param array $postarr An array of sanitized, but otherwise unmodified post data.
+		 * @param array $data                An array of slashed, sanitized, and processed post data.
+		 * @param array $postarr             An array of sanitized (and slashed) but otherwise unmodified post data.
+		 * @param array $unsanitized_postarr An array of slashed yet *unsanitized* and unprocessed post data as
+		 *                                   originally passed to wp_insert_post().
 		 */
-		$data = apply_filters( 'wp_insert_post_data', $data, $postarr );
+		$data = apply_filters( 'wp_insert_post_data', $data, $postarr, $unsanitized_postarr );
 	}
 	$data = wp_unslash( $data );
 	$where = array( 'ID' => $post_ID );
diff --git a/src/wp-includes/user.php b/src/wp-includes/user.php
index ef3bc57dea..c508eda23d 100644
--- a/src/wp-includes/user.php
+++ b/src/wp-includes/user.php
@@ -1692,7 +1692,7 @@ function wp_insert_user( $userdata ) {
 	$data = apply_filters( 'wp_pre_insert_user_data', $data, $update, $update ? (int) $ID : null );
 
 	if ( $update ) {
-		if ( $user_email !== $old_user_data->user_email ) {
+		if ( $user_email !== $old_user_data->user_email || $user_pass !== $old_user_data->user_pass ) {
 			$data['user_activation_key'] = '';
 		}
 		$wpdb->update( $wpdb->users, $data, compact( 'ID' ) );
diff --git a/tests/phpunit/tests/customize/manager.php b/tests/phpunit/tests/customize/manager.php
index 1cd2c0e8e6..ca4c3a8f59 100644
--- a/tests/phpunit/tests/customize/manager.php
+++ b/tests/phpunit/tests/customize/manager.php
@@ -1089,6 +1089,171 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		$this->assertCount( 3, wp_get_post_revisions( $manager->changeset_post_id() ) );
 	}
 
+	/**
+	 * Test saving changeset post without Kses or other content_save_pre filters mutating content.
+	 *
+	 * @covers WP_Customize_Manager::save_changeset_post()
+	 */
+	public function test_save_changeset_post_without_kses_corrupting_json() {
+		global $wp_customize;
+		$lesser_admin_user_id = self::factory()->user->create( array( 'role' => 'administrator' ) );
+
+		$uuid         = wp_generate_uuid4();
+		$wp_customize = new WP_Customize_Manager(
+			array(
+				'changeset_uuid' => $uuid,
+			)
+		);
+
+		add_filter( 'map_meta_cap', array( $this, 'filter_map_meta_cap_to_disallow_unfiltered_html' ), 10, 2 );
+		kses_init();
+		add_filter( 'content_save_pre', 'capital_P_dangit' );
+		add_post_type_support( 'customize_changeset', 'revisions' );
+
+		$options = array(
+			'custom_html_1' => '<script>document.write(" Wordpress 1")</script>',
+			'custom_html_2' => '<script>document.write(" Wordpress 2")</script>',
+			'custom_html_3' => '<script>document.write(" Wordpress 3")</script>',
+		);
+
+		// Populate setting as user who can bypass content_save_pre filter.
+		wp_set_current_user( self::$admin_user_id );
+		$wp_customize = $this->get_manager_for_testing_json_corruption_protection( $uuid );
+		$wp_customize->set_post_value( 'custom_html_1', $options['custom_html_1'] );
+		$wp_customize->save_changeset_post(
+			array(
+				'status' => 'draft',
+			)
+		);
+
+		// Populate setting as user who cannot bypass content_save_pre filter.
+		wp_set_current_user( $lesser_admin_user_id );
+		$wp_customize = $this->get_manager_for_testing_json_corruption_protection( $uuid );
+		$wp_customize->set_post_value( 'custom_html_2', $options['custom_html_2'] );
+		$wp_customize->save_changeset_post(
+			array(
+				'autosave' => true,
+			)
+		);
+
+		/*
+		 * Ensure that the unsanitized value (the "POST data") is preserved in the autosave revision.
+		 * The value is sent through the sanitize function when it is read from the changeset.
+		 */
+		$autosave_revision = wp_get_post_autosave( $wp_customize->changeset_post_id(), get_current_user_id() );
+		$saved_data        = json_decode( $autosave_revision->post_content, true );
+		$this->assertEquals( $options['custom_html_1'], $saved_data['custom_html_1']['value'] );
+		$this->assertEquals( $options['custom_html_2'], $saved_data['custom_html_2']['value'] );
+
+		// Update post to discard autosave.
+		$wp_customize->save_changeset_post(
+			array(
+				'status' => 'draft',
+			)
+		);
+
+		/*
+		 * Ensure that the unsanitized value (the "POST data") is preserved in the post content.
+		 * The value is sent through the sanitize function when it is read from the changeset.
+		 */
+		$wp_customize = $this->get_manager_for_testing_json_corruption_protection( $uuid );
+		$saved_data   = json_decode( get_post( $wp_customize->changeset_post_id() )->post_content, true );
+		$this->assertEquals( $options['custom_html_1'], $saved_data['custom_html_1']['value'] );
+		$this->assertEquals( $options['custom_html_2'], $saved_data['custom_html_2']['value'] );
+
+		/*
+		 * Ensure that the unsanitized value (the "POST data") is preserved in the revisions' content.
+		 * The value is sent through the sanitize function when it is read from the changeset.
+		 */
+		$revisions  = wp_get_post_revisions( $wp_customize->changeset_post_id() );
+		$revision   = array_shift( $revisions );
+		$saved_data = json_decode( $revision->post_content, true );
+		$this->assertEquals( $options['custom_html_1'], $saved_data['custom_html_1']['value'] );
+		$this->assertEquals( $options['custom_html_2'], $saved_data['custom_html_2']['value'] );
+
+		/*
+		 * Now when publishing the changeset, the unsanitized values will be read from the changeset
+		 * and sanitized according to the capabilities of the users who originally updated each
+		 * setting in the changeset to begin with.
+		 */
+		wp_set_current_user( $lesser_admin_user_id );
+		$wp_customize = $this->get_manager_for_testing_json_corruption_protection( $uuid );
+		$wp_customize->set_post_value( 'custom_html_3', $options['custom_html_3'] );
+		$wp_customize->save_changeset_post(
+			array(
+				'status' => 'publish',
+			)
+		);
+
+		// User saved as one who can bypass content_save_pre filter.
+		$this->assertContains( '<script>', get_option( 'custom_html_1' ) );
+		$this->assertContains( 'Wordpress', get_option( 'custom_html_1' ) ); // phpcs:ignore WordPress.WP.CapitalPDangit.Misspelled
+
+		// User saved as one who cannot bypass content_save_pre filter.
+		$this->assertNotContains( '<script>', get_option( 'custom_html_2' ) );
+		$this->assertContains( 'WordPress', get_option( 'custom_html_2' ) );
+
+		// User saved as one who also cannot bypass content_save_pre filter.
+		$this->assertNotContains( '<script>', get_option( 'custom_html_3' ) );
+		$this->assertContains( 'WordPress', get_option( 'custom_html_3' ) );
+	}
+
+	/**
+	 * Get a manager for testing JSON corruption protection.
+	 *
+	 * @param string $uuid UUID.
+	 * @return WP_Customize_Manager Manager.
+	 */
+	private function get_manager_for_testing_json_corruption_protection( $uuid ) {
+		global $wp_customize;
+		$wp_customize = new WP_Customize_Manager(
+			array(
+				'changeset_uuid' => $uuid,
+			)
+		);
+		for ( $i = 0; $i < 5; $i++ ) {
+			$wp_customize->add_setting(
+				sprintf( 'custom_html_%d', $i ),
+				array(
+					'type'              => 'option',
+					'sanitize_callback' => array( $this, 'apply_content_save_pre_filters_if_not_main_admin_user' ),
+				)
+			);
+		}
+		return $wp_customize;
+	}
+
+	/**
+	 * Sanitize content with Kses if the current user is not the main admin.
+	 *
+	 * @since 5.4.1
+	 *
+	 * @param string $content Content to sanitize.
+	 * @return string Sanitized content.
+	 */
+	public function apply_content_save_pre_filters_if_not_main_admin_user( $content ) {
+		if ( get_current_user_id() !== self::$admin_user_id ) {
+			$content = apply_filters( 'content_save_pre', $content );
+		}
+		return $content;
+	}
+
+	/**
+	 * Filter map_meta_cap to disallow unfiltered_html.
+	 *
+	 * @since 5.4.1
+	 *
+	 * @param array  $caps User's capabilities.
+	 * @param string $cap  Requested cap.
+	 * @return array Caps.
+	 */
+	public function filter_map_meta_cap_to_disallow_unfiltered_html( $caps, $cap ) {
+		if ( 'unfiltered_html' === $cap ) {
+			$caps = array( 'do_not_allow' );
+		}
+		return $caps;
+	}
+
 	/**
 	 * Call count for customize_changeset_save_data filter.
 	 *
diff --git a/tests/phpunit/tests/formatting/SanitizeFileName.php b/tests/phpunit/tests/formatting/SanitizeFileName.php
index d26b87134e..4db64c3c6a 100644
--- a/tests/phpunit/tests/formatting/SanitizeFileName.php
+++ b/tests/phpunit/tests/formatting/SanitizeFileName.php
@@ -67,4 +67,20 @@ class Tests_Formatting_SanitizeFileName extends WP_UnitTestCase {
 		// Test a filenames that becomes extensionless.
 		$this->assertEquals( 'no-extension', sanitize_file_name( '_.no-extension' ) );
 	}
+
+	/**
+	 * @dataProvider data_wp_filenames
+	 */
+	function test_replaces_invalid_utf8_characters( $input, $expected ) {
+		$this->assertEquals( $expected, sanitize_file_name( $input ) );
+	}
+
+	function data_wp_filenames() {
+		return array(
+			array( urldecode( '%B1myfile.png' ), 'myfile.png' ),
+			array( urldecode( '%B1myfile' ), 'myfile' ),
+			array( 'demo bar.png', 'demo-bar.png' ),
+			array( 'demo' . json_decode( '"\u00a0"' ) . 'bar.png', 'demo-bar.png' ),
+		);
+	}
 }
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index 0330016c5d..846999fdb5 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -917,7 +917,7 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertEquals( $u, wp_cache_get( $updated_user->user_nicename, 'userslugs' ) );
 	}
 
-	function test_changing_email_invalidates_password_reset_key() {
+	public function test_changing_email_invalidates_password_reset_key() {
 		global $wpdb;
 
 		$user = $this->author;
@@ -949,6 +949,26 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertEmpty( $user->user_activation_key );
 	}
 
+	public function test_changing_password_invalidates_password_reset_key() {
+		global $wpdb;
+
+		$user = $this->author;
+		$wpdb->update( $wpdb->users, array( 'user_activation_key' => 'key' ), array( 'ID' => $user->ID ) );
+		clean_user_cache( $user );
+
+		$user = get_userdata( $user->ID );
+		$this->assertEquals( 'key', $user->user_activation_key );
+
+		$userdata = array(
+			'ID'        => $user->ID,
+			'user_pass' => 'password',
+		);
+		wp_update_user( $userdata );
+
+		$user = get_userdata( $user->ID );
+		$this->assertEmpty( $user->user_activation_key );
+	}
+
 	public function test_search_users_login() {
 		$users = get_users( array( 'search' => 'user1', 'fields' => 'ID' ) );