diff --git a/src/wp-admin/includes/misc.php b/src/wp-admin/includes/misc.php
index 3724684ffd428..942f75b90e8e0 100644
--- a/src/wp-admin/includes/misc.php
+++ b/src/wp-admin/includes/misc.php
@@ -86,7 +86,9 @@ function extract_from_markers( $filename, $marker ) {
 				continue;
 			}
 
-			$result[] = $markerline;
+			if ( '' !== $markerline ) {
+				$result[] = $markerline;
+			}
 		}
 
 		if ( str_contains( $markerline, '# BEGIN ' . $marker ) ) {
diff --git a/tests/phpunit/tests/admin/includes/misc/extractFromMarkers.php b/tests/phpunit/tests/admin/includes/misc/extractFromMarkers.php
new file mode 100644
index 0000000000000..d40e210e30c06
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/misc/extractFromMarkers.php
@@ -0,0 +1,110 @@
+<?php
+
+/**
+ * Tests for the extract_from_markers() function.
+ *
+ * @group admin
+ *
+ * @covers ::extract_from_markers
+ */
+class Tests_extract_from_markers extends WP_UnitTestCase {
+
+	/**
+	 * Path to the temporary file used for testing.
+	 * @var string
+	 */
+	private $temp_file;
+
+	public function set_up() {
+		parent::set_up();
+		$this->temp_file = wp_tempnam( 'markers.txt' );
+	}
+
+	public function tear_down() {
+		if ( file_exists( $this->temp_file ) ) {
+			unlink( $this->temp_file );
+		}
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that extract_from_markers() correctly extracts content between markers.
+	 *
+	 * @ticket 65136
+	 *
+	 * @dataProvider data_extract_from_markers
+	 *
+	 * @param array  $expected The expected lines extracted.
+	 * @param string $content  The content of the file.
+	 * @param string $marker   The marker to extract.
+	 */
+	public function test_extract_from_markers( $expected, $content, $marker ) {
+		file_put_contents( $this->temp_file, $content );
+
+		$this->assertSame( $expected, extract_from_markers( $this->temp_file, $marker ) );
+	}
+
+	/**
+	 * Data provider for test_extract_from_markers.
+	 *
+	 * @return array[]
+	 */
+	public function data_extract_from_markers() {
+		return array(
+			'Empty file'                          => array(
+				'expected' => array(),
+				'content'  => '',
+				'marker'   => 'WordPress',
+			),
+			'Standard WordPress markers'          => array(
+				'expected' => array( 'Line 1', 'Line 2' ),
+				'content'  => "Outside\n# BEGIN WordPress\nLine 1\nLine 2\n# END WordPress\nOutside",
+				'marker'   => 'WordPress',
+			),
+			'Comments inside markers are ignored' => array(
+				'expected' => array( 'Real Line' ),
+				'content'  => "# BEGIN Test\n# Comment\nReal Line\n# END Test",
+				'marker'   => 'Test',
+			),
+			'Multiple marker blocks'              => array(
+				'expected' => array( 'Block 1', 'Block 2' ),
+				'content'  => "# BEGIN X\nBlock 1\n# END X\n# BEGIN X\nBlock 2\n# END X",
+				'marker'   => 'X',
+			),
+			'Marker not found'                    => array(
+				'expected' => array(),
+				'content'  => "Some content\nwithout markers",
+				'marker'   => 'WordPress',
+			),
+			'Partial markers'                     => array(
+				'expected' => array( 'Partial' ),
+				'content'  => "# BEGIN Y\nPartial",
+				'marker'   => 'Y',
+			),
+			'Full .htaccess example'              => array(
+				'expected' => array(
+					'<IfModule mod_rewrite.c>',
+					'RewriteEngine On',
+					'RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]',
+					'RewriteBase /',
+					'RewriteRule ^index\.php$ - [L]',
+					'RewriteCond %{REQUEST_FILENAME} !-f',
+					'RewriteCond %{REQUEST_FILENAME} !-d',
+					'RewriteRule . /index.php [L]',
+					'</IfModule>',
+				),
+				'content'  => "RewriteCond %{HTTPS} !=on\nRewriteCond %{HTTP:X-Forwarded-Proto} !=https\nRewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]\n\n# BEGIN WordPress\n# The directives (lines) between \"BEGIN WordPress\" and \"END WordPress\" are\n# dynamically generated, and should only be modified via WordPress filters.\n# Any changes to the directives between these markers will be overwritten.\n<IfModule mod_rewrite.c>\nRewriteEngine On\nRewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]\nRewriteBase /\nRewriteRule ^index\.php$ - [L]\nRewriteCond %{REQUEST_FILENAME} !-f\nRewriteCond %{REQUEST_FILENAME} !-d\nRewriteRule . /index.php [L]\n</IfModule>\n\n# END WordPress",
+				'marker'   => 'WordPress',
+			),
+		);
+	}
+
+	/**
+	 * Tests extraction when file does not exist.
+	 *
+	 * @ticket 65136
+	 */
+	public function test_extract_from_markers_non_existent_file() {
+		$this->assertSame( array(), extract_from_markers( '/non/existent/path', 'WordPress' ) );
+	}
+}