diff --git a/src/wp-includes/kses.php b/src/wp-includes/kses.php
index 025ef5d66bbde..3d35eb2c20f63 100644
--- a/src/wp-includes/kses.php
+++ b/src/wp-includes/kses.php
@@ -2591,21 +2591,23 @@ function _wp_add_global_attributes( $value ) {
  * @param string $url The URL to check.
  * @return bool True if the URL is safe, false otherwise.
  */
-function _wp_kses_allow_pdf_objects( $value ) {
+function _wp_kses_allow_pdf_objects( $url ) {
 	// We're not interested in URLs that contain query strings or fragments.
-	if ( strpos( $value, '?' ) !== false || strpos( $value, '#' ) !== false ) {
+	if ( strpos( $url, '?' ) !== false || strpos( $url, '#' ) !== false ) {
 		return false;
 	}
 
 	// If it doesn't have a PDF extension, it's not safe.
-	if ( 0 !== substr_compare( $value, '.pdf', -4, 4, true ) ) {
+	if ( 0 !== substr_compare( $url, '.pdf', -4, 4, true ) ) {
 		return false;
 	}
 
 	// If the URL host matches the current site's media URL, it's safe.
 	$upload_info = wp_upload_dir( null, false );
-	$upload_host = wp_parse_url( $upload_info['url'], PHP_URL_HOST );
-	if ( 0 === strpos( $value, "http://$upload_host/" ) || 0 === strpos( $value, "https://$upload_host/" ) ) {
+	$parsed_url  = wp_parse_url( $upload_info['url'] );
+	$upload_host = isset( $parsed_url['host'] ) ? $parsed_url['host'] : '';
+	$upload_port = isset( $parsed_url['port'] ) ? ':' . $parsed_url['port'] : '';
+	if ( 0 === strpos( $url, "http://$upload_host$upload_port/" ) || 0 === strpos( $url, "https://$upload_host$upload_port/" ) ) {
 		return true;
 	}
 
diff --git a/tests/phpunit/tests/kses.php b/tests/phpunit/tests/kses.php
index 8c857fe7d849b..cda6d3d7e44cc 100644
--- a/tests/phpunit/tests/kses.php
+++ b/tests/phpunit/tests/kses.php
@@ -1596,9 +1596,64 @@ function data_wp_kses_object_tag_allowed() {
 				'<object type="application/pdf" data="/cat/foo.pdf" />',
 				'',
 			),
+			'url with port number-like path'          => array(
+				'<object type="application/pdf" data="https://example.org/cat:8888/foo.pdf" />',
+				'<object type="application/pdf" data="https://example.org/cat:8888/foo.pdf" />',
+			),
 		);
 	}
 
+	/**
+	 * Test that object tags are allowed when there is a port number in the URL.
+	 *
+	 * @ticket 54261
+	 *
+	 * @dataProvider data_wp_kses_object_data_url_with_port_number_allowed
+	 *
+	 * @param string $html     A string of HTML to test.
+	 * @param string $expected The expected result from KSES.
+	 */
+	function test_wp_kses_object_data_url_with_port_number_allowed( $html, $expected ) {
+		add_filter( 'upload_dir', array( $this, 'wp_kses_upload_dir_filter' ), 10, 2 );
+		$this->assertSame( $expected, wp_kses_post( $html ) );
+	}
+
+	/**
+	 * Data provider for test_wp_kses_object_data_url_with_port_number_allowed().
+	 */
+	function data_wp_kses_object_data_url_with_port_number_allowed() {
+		return array(
+			'url with port number'                   => array(
+				'<object type="application/pdf" data="https://example.org:8888/cat/foo.pdf" />',
+				'<object type="application/pdf" data="https://example.org:8888/cat/foo.pdf" />',
+			),
+			'url with port number and http protocol' => array(
+				'<object type="application/pdf" data="http://example.org:8888/cat/foo.pdf" />',
+				'<object type="application/pdf" data="http://example.org:8888/cat/foo.pdf" />',
+			),
+			'url with wrong port number'             => array(
+				'<object type="application/pdf" data="http://example.org:3333/cat/foo.pdf" />',
+				'',
+			),
+			'url without port number'                => array(
+				'<object type="application/pdf" data="http://example.org/cat/foo.pdf" />',
+				'',
+			),
+		);
+	}
+
+	/**
+	 * Filter upload directory for tests using port number.
+	 *
+	 * @param  array $param See wp_upload_dir()
+	 * @return array        $param with a modified `url`.
+	 */
+	public function wp_kses_upload_dir_filter( $param ) {
+		$url_with_port_number = is_string( $param['url'] ) ? str_replace( 'example.org', 'example.org:8888', $param['url'] ) : $param['url'];
+		$param['url']         = $url_with_port_number;
+		return $param;
+	}
+
 	/**
 	 * Test that object tags will continue to function if they've been added using the
 	 * 'wp_kses_allowed_html' filter.