Rewrite Rules: Escape metacharacters in permastructs

src/wp-includes/class-wp-rewrite.php

@@ -912,6 +912,11 @@ public function generate_rewrite_rules( $permalink_structure, $ep_mask = EP_NONE
 
 		$num_tokens = count( $tokens[0] );
 
+		$quoted_rewritecode = array();
+		foreach ( $this->rewritecode as $code ) {
+			$quoted_rewritecode[] = preg_quote( $code, '#' );
+		}
+
 		$index          = $this->index; // Probably 'index.php'.
 		$feedindex      = $index;
 		$trackbackindex = $index;
@@ -960,7 +965,7 @@ public function generate_rewrite_rules( $permalink_structure, $ep_mask = EP_NONE
 			$struct  = ltrim( $struct, '/' );
 
 			// Replace tags with regexes.
-			$match = str_replace( $this->rewritecode, $this->rewritereplace, $struct );
+			$match = str_replace( $quoted_rewritecode, $this->rewritereplace, preg_quote( $struct, '#' ) );
 
 			// Make a list of tags, and store how many there are in $num_toks.
 			$num_toks = preg_match_all( '/%.+?%/', $struct, $toks );
@@ -1102,8 +1107,12 @@ public function generate_rewrite_rules( $permalink_structure, $ep_mask = EP_NONE
 					// Trim slashes from the end of the regex for this dir.
 					$match = rtrim( $match, '/' );
 
-					// Get rid of brackets.
-					$submatchbase = str_replace( array( '(', ')' ), '', $match );
+					// Remove capture groups from rewrite tag regexes for attachment rules.
+					$submatchbase = str_replace(
+						$quoted_rewritecode,
+						str_replace( array( '(', ')' ), '', $this->rewritereplace ),
+						preg_quote( rtrim( $struct, '/' ), '#' )
+					);
 
 					// Add a rule for at attachments, which take the form of <permalink>/some-text.
 					$sub1 = $submatchbase . '/([^/]+)/';

tests/phpunit/tests/rewrite.php

@@ -531,6 +531,70 @@ public function test_parse_request_with_post_slug_that_clashes_with_a_trashed_pa
 		$this->assertFalse( is_404() );
 	}
 
+	/**
+	 * @ticket 49510
+	 */
+	public function test_taxonomy_bases_with_regex_metacharacters() {
+		update_option( 'category_base', 'cat+base' );
+		update_option( 'tag_base', 'tag+base' );
+		create_initial_taxonomies();
+		delete_option( 'rewrite_rules' );
+
+		$category_id = self::factory()->term->create(
+			array(
+				'name'     => 'Category A',
+				'taxonomy' => 'category',
+			)
+		);
+		$tag_id      = self::factory()->term->create(
+			array(
+				'name'     => 'Tag A',
+				'taxonomy' => 'post_tag',
+			)
+		);
+
+		$this->go_to( get_term_link( $category_id, 'category' ) );
+		$category_name = get_query_var( 'category_name' );
+
+		$this->go_to( get_term_link( $tag_id, 'post_tag' ) );
+
+		$this->assertSame(
+			array( 'category-a', 'tag-a' ),
+			array( $category_name, get_query_var( 'tag' ) )
+		);
+	}
+
+	/**
+	 * @ticket 49510
+	 */
+	public function test_taxonomy_base_regex_metacharacter_is_literal() {
+		update_option( 'category_base', 'cat.base' );
+		create_initial_taxonomies();
+		delete_option( 'rewrite_rules' );
+
+		self::factory()->term->create(
+			array(
+				'name'     => 'Category A',
+				'taxonomy' => 'category',
+			)
+		);
+
+		$this->go_to( '/catXbase/category-a/' );
+
+		$this->assertSame( '', get_query_var( 'category_name' ) );
+	}
+
+	/**
+	 * @ticket 49510
+	 */
+	public function test_permalink_regex_metacharacters_are_literal_in_attachment_rules() {
+		global $wp_rewrite;
+
+		$rules = $wp_rewrite->generate_rewrite_rules( '/archive(2026)/%postname%/', EP_PERMALINK );
+
+		$this->assertSame( 'index.php?attachment=$matches[1]', $rules['archive\(2026\)/[^/]+/attachment/([^/]+)/?$'] );
+	}
+
 	/**
 	 * @ticket 29107
 	 */

tests/phpunit/tests/rewrite/rewriteTags.php

@@ -81,6 +81,19 @@ public function test_add_rewrite_tag_updates_existing() {
 		$this->assertNotContains( 'pagename=', $wp_rewrite->queryreplace );
 	}
 
+	/**
+	 * @ticket 49510
+	 */
+	public function test_generate_rewrite_rules_with_regex_metacharacter_in_tag() {
+		global $wp_rewrite;
+
+		add_rewrite_tag( '%foo.bar%', '([^/]+)', 'foo=' );
+
+		$rules = $wp_rewrite->generate_rewrite_rules( '/base/%foo.bar%' );
+
+		$this->assertSame( 'index.php?foo=$1', $rules['base/([^/]+)/?$'] );
+	}
+
 	public function test_remove_rewrite_tag() {
 		global $wp_rewrite;