diff --git a/wp-includes/class-wp-query.php b/wp-includes/class-wp-query.php
index f95cb6149f..f088bda6da 100644
--- a/wp-includes/class-wp-query.php
+++ b/wp-includes/class-wp-query.php
@@ -474,6 +474,16 @@ class WP_Query {
 
 	private $compat_methods = array( 'init_query_flags', 'parse_tax_query' );
 
+	/**
+	 * The cache key generated by the query.
+	 *
+	 * The cache key is generated by the method ::generate_cache_key() after the
+	 * query has been normalized.
+	 *
+	 * @var string
+	 */
+	private $query_cache_key = '';
+
 	/**
 	 * Resets query flags to false.
 	 *
@@ -1101,7 +1111,8 @@ class WP_Query {
 
 		if ( ! empty( $qv['post_type'] ) ) {
 			if ( is_array( $qv['post_type'] ) ) {
-				$qv['post_type'] = array_map( 'sanitize_key', $qv['post_type'] );
+				$qv['post_type'] = array_map( 'sanitize_key', array_unique( $qv['post_type'] ) );
+				sort( $qv['post_type'] );
 			} else {
 				$qv['post_type'] = sanitize_key( $qv['post_type'] );
 			}
@@ -1109,7 +1120,8 @@ class WP_Query {
 
 		if ( ! empty( $qv['post_status'] ) ) {
 			if ( is_array( $qv['post_status'] ) ) {
-				$qv['post_status'] = array_map( 'sanitize_key', $qv['post_status'] );
+				$qv['post_status'] = array_map( 'sanitize_key', array_unique( $qv['post_status'] ) );
+				sort( $qv['post_status'] );
 			} else {
 				$qv['post_status'] = preg_replace( '|[^a-z0-9_,-]|', '', $qv['post_status'] );
 			}
@@ -1182,9 +1194,12 @@ class WP_Query {
 
 				$term = $q[ $t->query_var ];
 
-				if ( is_array( $term ) ) {
-					$term = implode( ',', $term );
+				if ( ! is_array( $term ) ) {
+					$term = explode( ',', $term );
+					$term = array_map( 'trim', $term );
 				}
+				sort( $term );
+				$term = implode( ',', $term );
 
 				if ( str_contains( $term, '+' ) ) {
 					$terms = preg_split( '/[+]+/', $term );
@@ -1220,7 +1235,8 @@ class WP_Query {
 
 			$cat_array = preg_split( '/[,\s]+/', urldecode( $q['cat'] ) );
 			$cat_array = array_map( 'intval', $cat_array );
-			$q['cat']  = implode( ',', $cat_array );
+			sort( $cat_array );
+			$q['cat'] = implode( ',', $cat_array );
 
 			foreach ( $cat_array as $cat ) {
 				if ( $cat > 0 ) {
@@ -1262,7 +1278,8 @@ class WP_Query {
 
 		if ( ! empty( $q['category__in'] ) ) {
 			$q['category__in'] = array_map( 'absint', array_unique( (array) $q['category__in'] ) );
-			$tax_query[]       = array(
+			sort( $q['category__in'] );
+			$tax_query[] = array(
 				'taxonomy'         => 'category',
 				'terms'            => $q['category__in'],
 				'field'            => 'term_id',
@@ -1272,6 +1289,7 @@ class WP_Query {
 
 		if ( ! empty( $q['category__not_in'] ) ) {
 			$q['category__not_in'] = array_map( 'absint', array_unique( (array) $q['category__not_in'] ) );
+			sort( $q['category__not_in'] );
 			$tax_query[]           = array(
 				'taxonomy'         => 'category',
 				'terms'            => $q['category__not_in'],
@@ -1282,7 +1300,8 @@ class WP_Query {
 
 		if ( ! empty( $q['category__and'] ) ) {
 			$q['category__and'] = array_map( 'absint', array_unique( (array) $q['category__and'] ) );
-			$tax_query[]        = array(
+			sort( $q['category__and'] );
+			$tax_query[] = array(
 				'taxonomy'         => 'category',
 				'terms'            => $q['category__and'],
 				'field'            => 'term_id',
@@ -1300,10 +1319,12 @@ class WP_Query {
 
 		if ( '' !== $q['tag'] && ! $this->is_singular && $this->query_vars_changed ) {
 			if ( str_contains( $q['tag'], ',' ) ) {
+				// @todo Handle normalizing `tag` query string.
 				$tags = preg_split( '/[,\r\n\t ]+/', $q['tag'] );
 				foreach ( (array) $tags as $tag ) {
 					$tag                 = sanitize_term_field( 'slug', $tag, 0, 'post_tag', 'db' );
 					$q['tag_slug__in'][] = $tag;
+					sort( $q['tag_slug__in'] );
 				}
 			} elseif ( preg_match( '/[+\r\n\t ]+/', $q['tag'] ) || ! empty( $q['cat'] ) ) {
 				$tags = preg_split( '/[+\r\n\t ]+/', $q['tag'] );
@@ -1314,6 +1335,7 @@ class WP_Query {
 			} else {
 				$q['tag']            = sanitize_term_field( 'slug', $q['tag'], 0, 'post_tag', 'db' );
 				$q['tag_slug__in'][] = $q['tag'];
+				sort( $q['tag_slug__in'] );
 			}
 		}
 
@@ -1327,7 +1349,8 @@ class WP_Query {
 
 		if ( ! empty( $q['tag__in'] ) ) {
 			$q['tag__in'] = array_map( 'absint', array_unique( (array) $q['tag__in'] ) );
-			$tax_query[]  = array(
+			sort( $q['tag__in'] );
+			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms'    => $q['tag__in'],
 			);
@@ -1335,6 +1358,7 @@ class WP_Query {
 
 		if ( ! empty( $q['tag__not_in'] ) ) {
 			$q['tag__not_in'] = array_map( 'absint', array_unique( (array) $q['tag__not_in'] ) );
+			sort( $q['tag__not_in'] );
 			$tax_query[]      = array(
 				'taxonomy' => 'post_tag',
 				'terms'    => $q['tag__not_in'],
@@ -1344,7 +1368,8 @@ class WP_Query {
 
 		if ( ! empty( $q['tag__and'] ) ) {
 			$q['tag__and'] = array_map( 'absint', array_unique( (array) $q['tag__and'] ) );
-			$tax_query[]   = array(
+			sort( $q['tag__and'] );
+			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms'    => $q['tag__and'],
 				'operator' => 'AND',
@@ -1353,7 +1378,8 @@ class WP_Query {
 
 		if ( ! empty( $q['tag_slug__in'] ) ) {
 			$q['tag_slug__in'] = array_map( 'sanitize_title_for_query', array_unique( (array) $q['tag_slug__in'] ) );
-			$tax_query[]       = array(
+			sort( $q['tag_slug__in'] );
+			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms'    => $q['tag_slug__in'],
 				'field'    => 'slug',
@@ -1362,7 +1388,8 @@ class WP_Query {
 
 		if ( ! empty( $q['tag_slug__and'] ) ) {
 			$q['tag_slug__and'] = array_map( 'sanitize_title_for_query', array_unique( (array) $q['tag_slug__and'] ) );
-			$tax_query[]        = array(
+			sort( $q['tag_slug__and'] );
+			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms'    => $q['tag_slug__and'],
 				'field'    => 'slug',
@@ -2186,8 +2213,11 @@ class WP_Query {
 			$where          .= " AND {$wpdb->posts}.post_name = '" . $q['attachment'] . "'";
 		} elseif ( is_array( $q['post_name__in'] ) && ! empty( $q['post_name__in'] ) ) {
 			$q['post_name__in'] = array_map( 'sanitize_title_for_query', $q['post_name__in'] );
-			$post_name__in      = "'" . implode( "','", $q['post_name__in'] ) . "'";
-			$where             .= " AND {$wpdb->posts}.post_name IN ($post_name__in)";
+			// Duplicate array before sorting to allow for the orderby clause.
+			$post_name__in_for_where = array_unique( $q['post_name__in'] );
+			sort( $post_name__in_for_where );
+			$post_name__in = "'" . implode( "','", $post_name__in_for_where ) . "'";
+			$where        .= " AND {$wpdb->posts}.post_name IN ($post_name__in)";
 		}
 
 		// If an attachment is requested by number, let it supersede any post number.
@@ -2199,9 +2229,14 @@ class WP_Query {
 		if ( $q['p'] ) {
 			$where .= " AND {$wpdb->posts}.ID = " . $q['p'];
 		} elseif ( $q['post__in'] ) {
-			$post__in = implode( ',', array_map( 'absint', $q['post__in'] ) );
+			// Duplicate array before sorting to allow for the orderby clause.
+			$post__in_for_where = $q['post__in'];
+			$post__in_for_where = array_unique( array_map( 'absint', $post__in_for_where ) );
+			sort( $post__in_for_where );
+			$post__in = implode( ',', array_map( 'absint', $post__in_for_where ) );
 			$where   .= " AND {$wpdb->posts}.ID IN ($post__in)";
 		} elseif ( $q['post__not_in'] ) {
+			sort( $q['post__not_in'] );
 			$post__not_in = implode( ',', array_map( 'absint', $q['post__not_in'] ) );
 			$where       .= " AND {$wpdb->posts}.ID NOT IN ($post__not_in)";
 		}
@@ -2209,9 +2244,14 @@ class WP_Query {
 		if ( is_numeric( $q['post_parent'] ) ) {
 			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_parent = %d ", $q['post_parent'] );
 		} elseif ( $q['post_parent__in'] ) {
-			$post_parent__in = implode( ',', array_map( 'absint', $q['post_parent__in'] ) );
+			// Duplicate array before sorting to allow for the orderby clause.
+			$post_parent__in_for_where = $q['post_parent__in'];
+			$post_parent__in_for_where = array_unique( array_map( 'absint', $post_parent__in_for_where ) );
+			sort( $post_parent__in_for_where );
+			$post_parent__in = implode( ',', array_map( 'absint', $post_parent__in_for_where ) );
 			$where          .= " AND {$wpdb->posts}.post_parent IN ($post_parent__in)";
 		} elseif ( $q['post_parent__not_in'] ) {
+			sort( $q['post_parent__not_in'] );
 			$post_parent__not_in = implode( ',', array_map( 'absint', $q['post_parent__not_in'] ) );
 			$where              .= " AND {$wpdb->posts}.post_parent NOT IN ($post_parent__not_in)";
 		}
@@ -2341,6 +2381,7 @@ class WP_Query {
 		if ( ! empty( $q['author'] ) && '0' != $q['author'] ) {
 			$q['author'] = addslashes_gpc( '' . urldecode( $q['author'] ) );
 			$authors     = array_unique( array_map( 'intval', preg_split( '/[,\s]+/', $q['author'] ) ) );
+			sort( $authors );
 			foreach ( $authors as $author ) {
 				$key         = $author > 0 ? 'author__in' : 'author__not_in';
 				$q[ $key ][] = abs( $author );
@@ -2349,9 +2390,17 @@ class WP_Query {
 		}
 
 		if ( ! empty( $q['author__not_in'] ) ) {
-			$author__not_in = implode( ',', array_map( 'absint', array_unique( (array) $q['author__not_in'] ) ) );
+			if ( is_array( $q['author__not_in'] ) ) {
+				$q['author__not_in'] = array_unique( array_map( 'absint', $q['author__not_in'] ) );
+				sort( $q['author__not_in'] );
+			}
+			$author__not_in = implode( ',', (array) $q['author__not_in'] );
 			$where         .= " AND {$wpdb->posts}.post_author NOT IN ($author__not_in) ";
 		} elseif ( ! empty( $q['author__in'] ) ) {
+			if ( is_array( $q['author__in'] ) ) {
+				$q['author__in'] = array_unique( array_map( 'absint', $q['author__in'] ) );
+				sort( $q['author__in'] );
+			}
 			$author__in = implode( ',', array_map( 'absint', array_unique( (array) $q['author__in'] ) ) );
 			$where     .= " AND {$wpdb->posts}.post_author IN ($author__in) ";
 		}
@@ -2588,6 +2637,7 @@ class WP_Query {
 			if ( ! is_array( $q_status ) ) {
 				$q_status = explode( ',', $q_status );
 			}
+			sort( $q_status );
 			$r_status = array();
 			$p_status = array();
 			$e_status = array();
@@ -4902,6 +4952,33 @@ class WP_Query {
 		// Sort post types to ensure same cache key generation.
 		sort( $args['post_type'] );
 
+		/*
+		 * Sort arrays that can be used for ordering prior to cache key generation.
+		 *
+		 * These arrays are sorted in the query generator for the purposes of the
+		 * WHERE clause but the arguments are not modified as they can be used for
+		 * the orderby clase.
+		 *
+		 * Their use in the orderby clause will generate a different SQL query so
+		 * they can be sorted for the cache key generation.
+		 */
+		$sortable_arrays_with_int_values = array(
+			'post__in',
+			'post_parent__in',
+		);
+		foreach ( $sortable_arrays_with_int_values as $key ) {
+			if ( isset( $args[ $key ] ) && is_array( $args[ $key ] ) ) {
+				$args[ $key ] = array_unique( array_map( 'absint', $args[ $key ] ) );
+				sort( $args[ $key ] );
+			}
+		}
+
+		// Sort and unique the 'post_name__in' for cache key generation.
+		if ( isset( $args['post_name__in'] ) && is_array( $args['post_name__in'] ) ) {
+			$args['post_name__in'] = array_unique( $args['post_name__in'] );
+			sort( $args['post_name__in'] );
+		}
+
 		if ( isset( $args['post_status'] ) ) {
 			$args['post_status'] = (array) $args['post_status'];
 			// Sort post status to ensure same cache key generation.
@@ -4942,7 +5019,8 @@ class WP_Query {
 			$last_changed .= wp_cache_get_last_changed( 'terms' );
 		}
 
-		return "wp_query:$key:$last_changed";
+		$this->query_cache_key = "wp_query:$key:$last_changed";
+		return $this->query_cache_key;
 	}
 
 	/**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2b4a31adfb..6f132c009a 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59765';
+$wp_version = '6.8-alpha-59766';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.