diff --git a/rsscloud/notification-request.php b/rsscloud/notification-request.php
index 0eecf06..2690c4e 100644
--- a/rsscloud/notification-request.php
+++ b/rsscloud/notification-request.php
@@ -44,12 +44,6 @@ function rsscloud_hub_process_notification_request( ) {
 
 	$scheme = ( 443 === $port ) ? 'https://' : 'http://';
 
-	$allow_port = function ( $ports ) use ( $port ) {
-		$ports[] = $port;
-		return $ports;
-	};
-	add_filter( 'http_allowed_safe_ports', $allow_port );
-
 	if ( !empty( $_POST['domain'] ) ) {
 		$domain = str_replace( '@', '', sanitize_text_field( wp_unslash( $_POST['domain'] ) ) );
 		$notify_url = $domain . ':' . $port . $path;
@@ -66,8 +60,6 @@ function rsscloud_hub_process_notification_request( ) {
 		$result = wp_safe_remote_post( $notify_url, array( 'method' => 'POST', 'timeout' => RSSCLOUD_HTTP_TIMEOUT, 'user-agent' => RSSCLOUD_USER_AGENT, 'port' => $port, 'body' => array( 'url' => esc_url_raw( wp_unslash( $_POST['url1'] ) ) ) ) );
 	}
 
-	remove_filter( 'http_allowed_safe_ports', $allow_port );
-
 	if ( is_wp_error( $result ) )
 		rsscloud_notify_result( 'false', 'Error testing notification URL : ' . $result->get_error_message() );
 
diff --git a/rsscloud/readme.txt b/rsscloud/readme.txt
index 9a45ff2..fa5e697 100644
--- a/rsscloud/readme.txt
+++ b/rsscloud/readme.txt
@@ -1,7 +1,7 @@
 === Plugin Name ===
 Contributors: josephscott, automattic
 Tags: rss
-Requires at least: 2.8
+Requires at least: 3.6
 Tested up to: 7.0.0
 Stable tag: 0.5.1
 
@@ -15,11 +15,10 @@ Adds RSSCloud ( http://rsscloud.co/ ) capabilities to your RSS feed.
 
 = 0.5.1 =
 * Harden plugin files against direct access and escape values in the cloud element output
-* Allow notifications to subscribers using non-standard ports
+* Add the source:cloud element so newer feed readers get the https notification URL
 * Allow notifications to https subscribers if port 443 is specified
 * More reliable detection of failed notification requests
 * Reject subscription requests with no domain when the remote address is unavailable
-* Use port 443 in cloud tag when site is https                                       
 
 = 0.5.0 =
 * Updates to support PHP 8+
diff --git a/rsscloud/rsscloud.php b/rsscloud/rsscloud.php
index 5cae602..9c62c4c 100644
--- a/rsscloud/rsscloud.php
+++ b/rsscloud/rsscloud.php
@@ -23,6 +23,9 @@
 if ( !defined( 'RSSCLOUD_HTTP_TIMEOUT' ) )
 	define( 'RSSCLOUD_HTTP_TIMEOUT', 3 );
 
+if ( !defined( 'RSSCLOUD_SOURCE_NS' ) )
+	define( 'RSSCLOUD_SOURCE_NS', 'https://source.scripting.com/' );
+
 require dirname( __FILE__ ) . '/data-storage.php';
 
 if ( !function_exists( 'rsscloud_hub_process_notification_request' ) )
@@ -52,11 +55,11 @@ function rsscloud_parse_request( $wp ) {
 
 if ( !function_exists( 'rsscloud_notify_result' ) ) {
 function rsscloud_notify_result( $success, $msg ) {
-	$success = strip_tags( $success );
+	$success = wp_strip_all_tags( $success );
 	$success = ent2ncr( $success );
 	$success = esc_html( $success );
 
-	$msg = strip_tags( $msg );
+	$msg = wp_strip_all_tags( $msg );
 	$msg = ent2ncr( $msg );
 	$msg = esc_html( $msg );
 
@@ -73,13 +76,11 @@ function rsscloud_add_rss_cloud_element( ) {
 		return;
 	}
 
-	$cloud = parse_url( get_option( 'home' ) . '/?rsscloud=notify' );
+	$notify_url = get_option( 'home' ) . '/?rsscloud=notify';
 
-	if ( isset( $cloud['port'] ) ) {
-		$cloud['port'] = (int) $cloud['port'];
-	} else {
-		$cloud['port'] = ( isset( $cloud['scheme'] ) && 'https' === $cloud['scheme'] ) ? 443 : 80;
-	}
+	$cloud = parse_url( $notify_url );
+
+	$cloud['port'] = isset( $cloud['port'] ) ? (int) $cloud['port'] : 80;
 
 	$cloud['path']	.= "?{$cloud['query']}";
 
@@ -89,6 +90,17 @@ function rsscloud_add_rss_cloud_element( ) {
 	echo " path='" . esc_attr( $cloud['path'] ) . "' registerProcedure=''";
 	echo " protocol='http-post' />";
 	echo "\n";
+
+	// Newer feed readers use source:cloud, which carries the full notification
+	// URL and so can advertise https where the cloud element above cannot.
+	// The namespace is declared on the element rather than via the rss2_ns
+	// action: declaring it here scopes it to this element, so another plugin
+	// binding the source prefix on the rss tag can neither collide with this
+	// declaration nor rebind the prefix out from under it.
+	echo "<source:cloud xmlns:source='" . esc_attr( RSSCLOUD_SOURCE_NS ) . "'>";
+	echo esc_url( $notify_url );
+	echo '</source:cloud>';
+	echo "\n";
 }
 
 function rsscloud_generate_challenge( $length = 30 ) {
diff --git a/rsscloud/send-post-notifications.php b/rsscloud/send-post-notifications.php
index c9ba56a..63638ba 100644
--- a/rsscloud/send-post-notifications.php
+++ b/rsscloud/send-post-notifications.php
@@ -30,16 +30,8 @@ function rsscloud_send_post_notifications( $rss2_url = false ) {
 			if ( !empty( $url['port'] ) )
 				$port = $url['port'];
 
-			$allow_port = function ( $ports ) use ( $port ) {
-				$ports[] = (int) $port;
-				return $ports;
-			};
-			add_filter( 'http_allowed_safe_ports', $allow_port );
-
 			$result = wp_safe_remote_post( $notify_url, array( 'method' => 'POST', 'timeout' => RSSCLOUD_HTTP_TIMEOUT, 'user-agent' => RSSCLOUD_USER_AGENT, 'port' => $port, 'body' => array( 'url' => $rss2_url ) ) );
 
-			remove_filter( 'http_allowed_safe_ports', $allow_port );
-
 			do_action( 'rsscloud_send_notification' );
 
 			if ( !is_wp_error( $result ) )
diff --git a/tests/test-notification-request.php b/tests/test-notification-request.php
index 78305de..626ad3b 100644
--- a/tests/test-notification-request.php
+++ b/tests/test-notification-request.php
@@ -535,42 +535,6 @@ function ( $preempt, $args, $url ) {
 		$this->assertArrayHasKey( 'http://callback.example.com:9000/notify', $notify[ $this->feed_url ] );
 	}
 
-	public function test_nonstandard_port_is_whitelisted_for_url_validation() {
-		// No pre_http_request mock — wp_http_validate_url only runs when the
-		// request isn't short-circuited, and that's where
-		// http_allowed_safe_ports gets applied. Hook it at priority 999 so
-		// we observe what the plugin handed to the validator.
-		$observed_ports = array();
-		add_filter(
-			'http_allowed_safe_ports',
-			function ( $ports ) use ( &$observed_ports ) {
-				$observed_ports = $ports;
-				return $ports;
-			},
-			999
-		);
-
-		// Use a TEST-NET-3 IP (RFC 5737) so wp_http_validate_url skips DNS
-		// and reaches the port check where our filter runs.
-		$_POST = array(
-			'url1'   => $this->feed_url,
-			'port'   => '4000',
-			'path'   => '/feedupdated',
-			'domain' => '203.0.113.5',
-		);
-
-		// Request will fail at the network layer (connection refused); we
-		// don't care about the outcome, only that validation was reached
-		// with our port whitelisted.
-		$this->call_process_notification_request();
-
-		$this->assertContains(
-			4000,
-			$observed_ports,
-			'Plugin should add the subscriber port to http_allowed_safe_ports before sending.'
-		);
-	}
-
 	public function test_port_443_uses_https_scheme_for_domain_based() {
 		add_filter(
 			'pre_http_request',
diff --git a/tests/test-rsscloud.php b/tests/test-rsscloud.php
index 939af50..1b0d52b 100644
--- a/tests/test-rsscloud.php
+++ b/tests/test-rsscloud.php
@@ -76,14 +76,14 @@ public function test_add_rss_cloud_element_uses_port_from_home_url() {
 		$this->assertStringContainsString( "port='" . $port . "'", $output );
 	}
 
-	public function test_add_rss_cloud_element_defaults_port_to_443_for_https_home() {
+	public function test_add_rss_cloud_element_escapes_attribute_values() {
 		$this->go_to( get_feed_link( 'rss2' ) );
 
 		// Override home AFTER go_to so is_feed() still works.
 		add_filter(
 			'option_home',
 			function () {
-				return 'https://example.com';
+				return 'http://example.com:8080/path?a=1&b=2';
 			}
 		);
 
@@ -91,17 +91,50 @@ function () {
 		rsscloud_add_rss_cloud_element();
 		$output = ob_get_clean();
 
-		$this->assertStringContainsString( "port='443'", $output );
+		// With proper escaping, '&' in attribute values should become '&amp;'.
+		$this->assertStringNotContainsString( '&b=2', $output,
+			'Attribute values must be escaped; raw & should not appear' );
+		$this->assertStringContainsString( '&amp;', $output,
+			'Attribute values should use esc_attr() which converts & to &amp;' );
 	}
 
-	public function test_add_rss_cloud_element_escapes_attribute_values() {
+	public function test_add_rss_cloud_element_outputs_source_cloud_tag() {
+		$this->go_to( get_feed_link( 'rss2' ) );
+
+		ob_start();
+		rsscloud_add_rss_cloud_element();
+		$output = ob_get_clean();
+
+		$this->assertStringContainsString( '<source:cloud ', $output );
+		$this->assertStringContainsString( '</source:cloud>', $output );
+		$this->assertStringContainsString( 'rsscloud=notify', $output );
+	}
+
+	public function test_source_cloud_declares_namespace_on_the_element() {
+		$this->go_to( get_feed_link( 'rss2' ) );
+
+		ob_start();
+		rsscloud_add_rss_cloud_element();
+		$output = ob_get_clean();
+
+		// The namespace must be declared on the element itself, not left to
+		// the rss2_ns action, so another plugin binding the source prefix on
+		// the rss tag cannot collide with it or rebind it.
+		$this->assertStringContainsString(
+			"xmlns:source='https://source.scripting.com/'",
+			$output,
+			'source:cloud must carry its own namespace declaration'
+		);
+	}
+
+	public function test_source_cloud_uses_full_url_with_site_scheme() {
 		$this->go_to( get_feed_link( 'rss2' ) );
 
 		// Override home AFTER go_to so is_feed() still works.
 		add_filter(
 			'option_home',
 			function () {
-				return 'http://example.com:8080/path?a=1&b=2';
+				return 'https://secure.example.com';
 			}
 		);
 
@@ -109,11 +142,69 @@ function () {
 		rsscloud_add_rss_cloud_element();
 		$output = ob_get_clean();
 
-		// With proper escaping, '&' in attribute values should become '&amp;'.
+		// The point of source:cloud: it carries the https endpoint that the
+		// port-80 / http-post cloud element above cannot express.
+		$this->assertStringContainsString(
+			'>https://secure.example.com/?rsscloud=notify</source:cloud>',
+			$output
+		);
+
+		// The classic cloud element must stay on port 80 / http-post for
+		// older readers such as FeedLand.
+		$this->assertStringContainsString( "port='80'", $output );
+		$this->assertStringContainsString( "protocol='http-post'", $output );
+	}
+
+	public function test_source_cloud_url_is_escaped() {
+		$this->go_to( get_feed_link( 'rss2' ) );
+
+		add_filter(
+			'option_home',
+			function () {
+				return 'https://example.com/path?a=1&b=2';
+			}
+		);
+
+		ob_start();
+		rsscloud_add_rss_cloud_element();
+		$output = ob_get_clean();
+
+		// Raw & is not well-formed XML in element content.
 		$this->assertStringNotContainsString( '&b=2', $output,
-			'Attribute values must be escaped; raw & should not appear' );
-		$this->assertStringContainsString( '&amp;', $output,
-			'Attribute values should use esc_attr() which converts & to &amp;' );
+			'source:cloud URL must be escaped; raw & should not appear' );
+	}
+
+	public function test_feed_with_source_cloud_is_well_formed_xml() {
+		$this->go_to( get_feed_link( 'rss2' ) );
+
+		ob_start();
+		rsscloud_add_rss_cloud_element();
+		$output = ob_get_clean();
+
+		// Wrap the fragment the way feed-rss2.php does, including another
+		// plugin binding the source prefix to a DIFFERENT uri on the rss tag,
+		// and confirm the result still parses and resolves correctly.
+		$xml = '<?xml version="1.0"?>'
+			. '<rss version="2.0" xmlns:source="https://example.invalid/other/">'
+			. '<channel><title>t</title>' . $output . '</channel></rss>';
+
+		$prev = libxml_use_internal_errors( true );
+		libxml_clear_errors();
+		$doc = simplexml_load_string( $xml );
+		$errors = libxml_get_errors();
+		libxml_clear_errors();
+		libxml_use_internal_errors( $prev );
+
+		$this->assertNotFalse( $doc, 'Feed fragment must be well-formed XML' );
+		$this->assertEmpty( $errors, 'Feed fragment must parse without XML errors' );
+
+		// The inline declaration must win over the rss tag's binding.
+		$source = $doc->channel->children( 'https://source.scripting.com/' );
+		$this->assertNotEmpty(
+			(string) $source->cloud,
+			'source:cloud must resolve to the scripting.com namespace, not the rss tag binding'
+		);
+		$this->assertStringContainsString( 'rsscloud=notify', (string) $source->cloud );
 	}
 
 	public function test_parse_request_does_nothing_without_rsscloud_var() {
diff --git a/tests/test-send-post-notifications.php b/tests/test-send-post-notifications.php
index c903628..62115b0 100644
--- a/tests/test-send-post-notifications.php
+++ b/tests/test-send-post-notifications.php
@@ -274,37 +274,4 @@ function () use ( &$fired ) {
 
 		$this->assertTrue( $fired );
 	}
-
-	public function test_nonstandard_port_is_whitelisted_for_url_validation() {
-		// No pre_http_request mock — we want wp_http_validate_url to run so
-		// the plugin's http_allowed_safe_ports filter gets applied. Hook at
-		// priority 999 to observe what the validator sees.
-		$observed_ports = array();
-		add_filter(
-			'http_allowed_safe_ports',
-			function ( $ports ) use ( &$observed_ports ) {
-				$observed_ports = $ports;
-				return $ports;
-			},
-			999
-		);
-
-		// TEST-NET-3 IP (RFC 5737) — wp_http_validate_url skips DNS for
-		// literal IPs and reaches the port check where our filter fires.
-		$this->set_notifications(
-			$this->build_notifications(
-				array(
-					'notify_url' => 'http://203.0.113.5:4000/feedupdated',
-				)
-			)
-		);
-
-		rsscloud_send_post_notifications( $this->feed_url );
-
-		$this->assertContains(
-			4000,
-			$observed_ports,
-			'Plugin should add the subscriber port to http_allowed_safe_ports before sending.'
-		);
-	}
 }