diff --git a/src/wp-includes/feed.php b/src/wp-includes/feed.php
index 7ef7059ce45bd..810abfee6fa2d 100644
--- a/src/wp-includes/feed.php
+++ b/src/wp-includes/feed.php
@@ -482,6 +482,10 @@ function rss_enclosure() {
 			foreach ( (array) $val as $enc ) {
 				$enclosure = explode( "\n", $enc );
 
+				if ( count( $enclosure ) < 3 ) {
+					continue;
+				}
+
 				// Only get the first element, e.g. 'audio/mpeg' from 'audio/mpeg mpga mp2 mp3'.
 				$t    = preg_split( '/[ \t]/', trim( $enclosure[2] ) );
 				$type = $t[0];
diff --git a/tests/phpunit/tests/feed/rssEnclosure.php b/tests/phpunit/tests/feed/rssEnclosure.php
new file mode 100644
index 0000000000000..37aca73f2b830
--- /dev/null
+++ b/tests/phpunit/tests/feed/rssEnclosure.php
@@ -0,0 +1,139 @@
+<?php
+
+/**
+ * Test the feed.
+ *
+ * @group feed
+ */
+class Tests_rssEnclosure extends WP_UnitTestCase {
+	/**
+	 * @ticket 58798
+	 *
+	 * @covers ::rss_enclosure
+	 */
+	public function test_rss_enclosure_filter() {
+		$post_id         = self::factory()->post->create();
+		$GLOBALS['post'] = $post_id;
+
+		$valid_enclosure_string = "http://example.com/sound2.mp3\n12345\naudio/mpeg\n";
+
+		update_post_meta( $post_id, 'enclosure', $valid_enclosure_string );
+
+		add_filter(
+			'rss_enclosure',
+			function () {
+				return 'filtered_html_link_tag';
+			}
+		);
+
+		$this->assertSame( 'filtered_html_link_tag', get_echo( 'rss_enclosure' ), 'The `rss_enclosure` filter could not be applied.' );
+	}
+
+	/**
+	 * @ticket 58798
+	 *
+	 * @covers ::rss_enclosure
+	 */
+	public function test_rss_enclosure_when_global_post_is_empty() {
+		$this->assertEmpty( get_echo( 'rss_enclosure' ), 'It should return empty when the global post is not set.' );
+	}
+
+	/**
+	 * @ticket 58798
+	 *
+	 * @covers ::rss_enclosure
+	 */
+	public function test_rss_enclosure_when_enclosure_meta_field_is_empty() {
+		$post_id         = self::factory()->post->create();
+		$GLOBALS['post'] = $post_id;
+
+		$this->assertEmpty( get_echo( 'rss_enclosure' ), 'The global post does not have the `enclosure` meta field and should return empty. ' );
+	}
+
+	/**
+	 * @ticket 58798
+	 *
+	 * @dataProvider data_rss_enclosure_with_multiline_enclosure_string
+	 * @covers ::rss_enclosure
+	 */
+	public function test_rss_enclosure_with_multiline_enclosure_string( $enclosure_data, $enclosure_string ) {
+		$post_id         = self::factory()->post->create();
+		$GLOBALS['post'] = $post_id;
+
+		update_post_meta( $post_id, 'enclosure', $enclosure_string );
+
+		$expected = '<enclosure url="' . $enclosure_data['url'] . '" length="' . $enclosure_data['length'] . '" type="' . $enclosure_data['type'] . '" />' . "\n";
+
+		$this->assertSame( $expected, get_echo( 'rss_enclosure' ), 'It should return a valid enclosure tag. ' );
+	}
+
+	/**
+	 * Data provider for valid enclosure string.
+	 *
+	 * @return array[].
+	 */
+	public function data_rss_enclosure_with_multiline_enclosure_string() {
+		return array(
+			'two-break-lines'         => array(
+				array(
+					'url'    => 'http://example.com/sound2.mp3',
+					'length' => 12345,
+					'type'   => 'audio/mpeg',
+				),
+				"http://example.com/sound2.mp3\n12345\naudio/mpeg",
+			),
+			'three-break-lines'       => array(
+				array(
+					'url'    => 'http://example.com/sound2.mp3',
+					'length' => 12345,
+					'type'   => 'audio/mpeg',
+				),
+				"http://example.com/sound2.mp3\n12345\naudio/mpeg\n",
+			),
+			'extra-break-line-at-end' => array(
+				array(
+					'url'    => 'http://example.com/sound2.mp3',
+					'length' => 12345,
+					'type'   => 'audio/mpeg',
+				),
+				"http://example.com/sound2.mp3\n12345\naudio/mpeg\n\n",
+			),
+			'extra-type-elements'     => array(
+				array(
+					'url'    => 'http://example.com/sound2.mp3',
+					'length' => 12345,
+					'type'   => 'audio/mpeg',
+				),
+				"http://example.com/sound2.mp3\n12345\naudio/mpeg mpga mp2 mp3\n",
+			),
+		);
+	}
+
+	/**
+	 * @ticket 58798
+	 *
+	 * @dataProvider data_rss_enclosure_with_non_valid_enclosure_string
+	 * @covers ::rss_enclosure
+	 */
+	public function test_rss_enclosure_with_non_valid_enclosure_string( $enclosure_string ) {
+		$post_id         = self::factory()->post->create();
+		$GLOBALS['post'] = $post_id;
+
+		update_post_meta( $post_id, 'enclosure', $enclosure_string );
+
+		$this->assertEmpty( get_echo( 'rss_enclosure' ), 'It should return empty when the `enclosure` meta field is not saved in a multiline string.' );
+	}
+
+	/**
+	 * Data provider for non-valid enclosure string.
+	 *
+	 * @return array[].
+	 */
+	public function data_rss_enclosure_with_non_valid_enclosure_string() {
+		return array(
+			'empty'          => array( '' ),
+			'no-break-lines' => array( 'http://example.com/sound2.mp3 12345 audio/mpeg' ),
+			'one-break-line' => array( "http://example.com/sound2.mp3\n12345 audio/mpeg" ),
+		);
+	}
+}