diff --git a/classes/admin/class-slack-settings.php b/classes/admin/class-slack-settings.php
index 125e0cdd4..98e55835f 100644
--- a/classes/admin/class-slack-settings.php
+++ b/classes/admin/class-slack-settings.php
@@ -13,35 +13,39 @@
 class Slack_Settings {
 
 	/**
-	 * The Slack client ID.
+	 * The Progress Planner API root URL.
 	 *
 	 * @var string
 	 */
-	const CLIENT_ID = '3300596017925.8228567943589';
+	const API_ROOT = 'https://prpl.fyi/api/v1';
 
 	/**
-	 * The Slack client secret.
+	 * The Progress Planner OAuth endpoint.
 	 *
 	 * @var string
 	 */
-	const CLIENT_SECRET = '79dfe36cd83b4be906d1c8f5906923be';
+	const OAUTH_ENDPOINT = '/slack/oauth';
 
 	/**
-	 * The redirect URI for the Slack OAuth callback.
+	 * Get the authorization URL for Slack OAuth.
 	 *
-	 * @var string
+	 * @return string
 	 */
-	public $redirect_uri;
+	private function get_auth_url() {
+		$site_url = \admin_url( 'admin.php?page=progress-planner-slack' );
+		$params = [
+			'site_url' => \rawurlencode( $site_url ),
+			'site_name' => \rawurlencode( \get_bloginfo( 'name' ) ),
+		];
+
+		return self::API_ROOT . self::OAUTH_ENDPOINT . '?' . \http_build_query( $params );
+	}
 
 	/**
 	 * Constructor.
 	 */
 	public function __construct() {
 
-		$this->redirect_uri = \defined( 'PROGRESS_PLANNER_SLACK_DEBUG' ) && \PROGRESS_PLANNER_SLACK_DEBUG
-			? 'https://a549-146-212-36-44.ngrok-free.app/wp-admin/admin.php?page=progress-planner-slack&slack_oauth=1'
-			: admin_url( 'admin.php?page=progress-planner-slack&slack_oauth=1' );
-
 		// Add the admin submenu page.
 		\add_action( 'admin_menu', [ $this, 'add_admin_menu_page' ], 99 );
 		\add_action( 'admin_init', [ $this, 'handle_oauth_callback' ] );
@@ -71,28 +75,12 @@ public function add_admin_menu_page() {
 	 * Handle the OAuth callback from Slack.
 	 */
 	public function handle_oauth_callback() {
-		if ( ! isset( $_GET['slack_oauth'] ) || ! isset( $_GET['code'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
+		if ( ! isset( $_GET['slack_token'] ) ) {
 			return;
 		}
 
-		$response = wp_remote_post(
-			'https://slack.com/api/oauth.v2.access',
-			[
-				'body' => [
-					'client_id'     => self::CLIENT_ID,
-					'client_secret' => self::CLIENT_SECRET,
-					'code'          => sanitize_text_field( wp_unslash( $_GET['code'] ) ), // phpcs:ignore WordPress.Security.NonceVerification.Recommended
-					'redirect_uri'  => $this->redirect_uri,
-				],
-			]
-		);
-
-		if ( ! is_wp_error( $response ) ) {
-			$body = json_decode( wp_remote_retrieve_body( $response ), true );
-			if ( ! empty( $body['access_token'] ) ) {
-				update_option( 'slack_access_token', $body['access_token'] );
-			}
-		}
+		$token = sanitize_text_field( wp_unslash( $_GET['slack_token'] ) );
+		update_option( 'slack_access_token', $token );
 
 		wp_safe_redirect( admin_url( 'admin.php?page=progress-planner-slack' ) );
 		exit;
@@ -136,7 +124,7 @@ public function render_page() {
 				<?php if ( empty( $access_token ) ) : ?>
 					<p><?php esc_html_e( 'Not connected to Slack', 'progress-planner' ); ?></p>
 					<?php
-					$auth_url = 'https://slack.com/oauth/v2/authorize?client_id=' . self::CLIENT_ID . '&scope=chat:write,channels:read&redirect_uri=' . rawurlencode( $this->redirect_uri );
+					$auth_url = $this->get_auth_url();
 					?>
 					<p>
 						<a href="<?php echo esc_url( $auth_url ); ?>" class="button button-primary">
diff --git a/classes/class-slack-notification.php b/classes/class-slack-notification.php
index 97b8fd22b..c9fff999b 100644
--- a/classes/class-slack-notification.php
+++ b/classes/class-slack-notification.php
@@ -20,12 +20,20 @@ class Slack_Notification {
 	 */
 	public static function send_notification( $message ) {
 		$access_token = get_option( 'slack_access_token' );
+		$access_token = self::decrypt_token( $access_token );
 		$channel      = get_option( 'slack_channel' );
 
 		if ( empty( $access_token ) || empty( $channel ) ) {
 			return false;
 		}
 
+		// Update last used timestamp on progressplanner.com
+		wp_remote_post( 'https://prpl.fyi/api/v1/slack/ping', [
+			'body' => [
+				'site_url' => admin_url(),
+			],
+		] );
+
 		$response = wp_remote_post(
 			'https://slack.com/api/chat.postMessage',
 			[
@@ -55,4 +63,20 @@ public static function send_notification( $message ) {
 
 		return ! empty( $body['ok'] );
 	}
+
+	/**
+	 * Decrypt the stored token.
+	 *
+	 * @param string $encrypted_token The encrypted token.
+	 * @return string
+	 */
+	private static function decrypt_token( $encrypted_token ) {
+		$data = base64_decode( $encrypted_token );
+		$iv_length = openssl_cipher_iv_length( 'aes-256-cbc' );
+
+		$iv = substr( $data, 0, $iv_length );
+		$encrypted = substr( $data, $iv_length );
+
+		return openssl_decrypt( $encrypted, 'aes-256-cbc', ENCRYPTION_KEY, 0, $iv );
+	}
 }