Reflected XSS in https://███████ via hidden parameter "████████"

Hi everyone :) I found a Reflected XSS on https://███████ via hidden parameter "████████" on the following authentication page : https://███████/██████████ ## Steps To Reproduce: - Use your favorite web browser - Go to : ``` https://███████/███████&███=TEST%22%3E%3Cscript%3Ealert(%27Reflected%20XSS%27)%3C/script%3E ``` An XSS is triggered ! The initial page was https://█████████/█████████ With a little research, you can find a hidden parameter "████████" which is directly reflected in the source code **without sanitize user entries**. Then just close the tag and inject our malicious code. ## Supporting Material/References: Work on every browser (Firefox, Chrome ..) ## Suggested Mitigation/Remediation Actions - Never trust user inputs, and therefore sanitize them. - If the parameter "███" is useless in this page and in the authentication process, then it should be deleted. ## Impact The damages of a reflexive XSS flaw are numerous: executing malicious javascript code, phishing, defacing ... We can also inject HTML code and mislead the user when displaying the web page. From [OWASP](https://owasp.org/www-community/attacks/xss/) : >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.