During an internal audit of the All In One SEO plugin, we uncovered an SQL Injection vulnerability and a Privilege Escalation bug.

If exploited, the SQL Injection vulnerability could grant attackers access to privileged information from the affected site's database (e.g., usernames and hashed passwords).

The Privilege Escalation bug we discovered may grant bad actors access to protected REST API endpoints they shouldn't have access to. This could ultimately enable users with low-privileged accounts, like subscribers, to perform remote code execution on affected sites.

We reported the vulnerabilities to the plugin's author via email, and they recently released version 4.1.5.3 to address them. We strongly recommend that you update to the latest plugin version and have an established security solution on your site, such as Jetpack Security.

Details

Plugin Name: All In One SEO
Plugin URI: https://wordpress.org/plugins/all-in-one-seo-pack/
Author: https://aioseo.com/

The Vulnerabilities

Authenticated Privilege Escalation

Affected versions: Every version between 4.0.0 and 4.1.5.2 inclusively.
CVE-ID: CVE-2021-25036
CVSSv3.1: 9.9
CWSS: 92.1

 	/** 	 * Validates access from the routes array. 	 * 	 * @since 4.0.0 	 * 	 * @param  \WP_REST_Request $request The REST Request. 	 * @return bool                      True if validated, false if not. 	 */ 	public function validateAccess( $request ) { 		$route     = str_replace( '/' . $this->namespace . '/', '', $request->get_route() ); 		$routeData = isset( $this->getRoutes()[ $request->get_method() ][ $route ] ) ? $this->getRoutes()[ $request->get_method() ][ $route ] : [];  		// No direct route name, let's try the regexes. 		if ( empty( $routeData ) ) { 			foreach ( $this->getRoutes()[ $request->get_method() ] as $routeRegex => $routeInfo ) { 				$routeRegex = str_replace( '@', '\@', $routeRegex ); 				if ( preg_match( "@{$routeRegex}@", $route ) ) { 					$routeData = $routeInfo; 					break; 				} 			} 		}  		if ( empty( $routeData['access'] ) ) { 			return true; 		}  		// We validate with any of the access options. 		if ( ! is_array( $routeData['access'] ) ) { 			$routeData['access'] = [ $routeData['access'] ]; 		} 		foreach ( $routeData['access'] as $access ) { 			if ( current_user_can( $access ) ) { 				return true; 			} 		}  		if ( current_user_can( apply_filters( 'aioseo_manage_seo', 'aioseo_manage_seo' ) ) ) { 			return true; 		}  		return false; 	}

The privilege checks applied by All In One SEO to secure REST API endpoints contained a very subtle bug that could've granted users with low-privileged accounts (like subscribers) access to every single endpoint the plugin registers. 

The Api::validateAccess() method relies on the REST API route being requested to know which privilege checks to enforce on a given request. Since it didn't account for the fact that WordPress treats REST API routes as case-insensitive strings, changing a single character to uppercase would completely bypass the privilege checks routine.

This is particularly worrying because some of the plugin's endpoints are pretty sensitive. For example, the aioseo/v1/htaccess endpoint can rewrite a site's .htaccess with arbitrary content. An attacker could abuse this feature to hide .htaccess backdoors and execute malicious code on the server.

Authenticated SQL Injection

Affected versions: Every version between 4.1.3.1 and 4.1.5.2 inclusively.
CVE-ID: CVE-2021-25037
CVSSv3.1: 7.7
CWSS: 80.4

 /**  * Searches for posts or terms by ID/name.  *  * @since 4.0.0  *  * @param  \WP_REST_Request  $request The REST Request  * @return \WP_REST_Response          The response.  */ public static function searchForObjects( $request ) {     $body = $request->get_json_params();       if ( empty( $body['query'] ) ) {         return new \WP_REST_Response( [             'success' => false,             'message' => 'No search term was provided.'         ], 400 );     }     if ( empty( $body['type'] ) ) {         return new \WP_REST_Response( [             'success' => false,             'message' => 'No type was provided.'         ], 400 );     }       $searchQuery = aioseo()->db->db->esc_like( $body['query'] );       $objects        = [];     $dynamicOptions = aioseo()->dynamicOptions->noConflict();     if ( 'posts' === $body['type'] ) {           $postTypes = aioseo()->helpers->getPublicPostTypes( true );         foreach ( $postTypes as $postType ) {             // Check if post type isn't noindexed.             if ( $dynamicOptions->searchAppearance->postTypes->has( $postType ) && ! $dynamicOptions->searchAppearance->postTypes->$postType->show ) {                 $postTypes = aioseo()->helpers->unsetValue( $postTypes, $postType );             }         }           $objects = aioseo()->db             ->start( 'posts' )             ->select( 'ID, post_type, post_title, post_name' )             ->whereRaw( "( post_title LIKE '%{$searchQuery}%' OR post_name LIKE '%{$searchQuery}%' OR ID = '{$searchQuery}' )" )             ->whereIn( 'post_type', $postTypes )             ->whereIn( 'post_status', [ 'publish', 'draft', 'future', 'pending' ] )             ->orderBy( 'post_title' )             ->limit( 10 )             ->run()             ->result();

The PostsTerms::searchForObjects() method, which is accessible via the /wp-json/aioseo/v1/objects REST API route only escaped user input using wpdb::esc_like() before appending said input to an SQL query. Since this method isn't designed to escape quotes, an attacker could still inject them and force the query to leak sensitive information from the database, like user credentials.

While this endpoint wasn't meant to be accessible to users with low-privileged accounts, the aforementioned privilege escalation attack vector made it possible for them to abuse this vulnerability.

Timeline

2021-12-01 – Initial contact with All In One SEO
2021-12-02 – We send them details about these vulnerabilities
2021-12-08 - All In One SEO 4.1.5.3 is released

Conclusion

We recommend that you check which version of the All In One SEO plugin your site is using, and if it is within the affected range, update it as soon as possible! 

At Jetpack, we work hard to make sure your websites are protected from these types of vulnerabilities. We recommend that you have a security plan for your site that includes malicious file scanning and backups. Jetpack Security is one great WordPress security option to ensure your site and visitors are safe.

Credits

Original researcher: Marc Montpas

Thanks to the rest of the Jetpack Scan team for feedback, help, and corrections.