Fighting Against XSS Attacks: A Usability Evaluation of OWASP ESAPI Output Encoding

TL;DR

This study evaluates the usability of OWASP ESAPI's output encoding to prevent XSS attacks, revealing common mistakes and usability issues that hinder effective protection in web applications.

Contribution

It provides an empirical analysis of programmers' mistakes and usability issues in OWASP ESAPI, offering recommendations for improving API usability to enhance security.

Findings

Programmers made 3 common mistakes in encoding

Identified 16 usability issues in OWASP ESAPI

Usability issues contribute to ineffective XSS prevention

Abstract

Cross Site Scripting (XSS) is one of the most critical vulnerabilities exist in web applications. XSS can be prevented by encoding untrusted data that are loaded into browser content of web applications. Security Application Programming Interfaces (APIs) such as OWASP ESAPI provide output encoding functionalities for programmers to use to protect their applications from XSS attacks. However, XSS still being ranked as one of the most critical vulnerabilities in web applications suggests that programmers are not effectively using those APIs to encode untrusted data. Therefore, we conducted an experimental study with 10 programmers where they attempted to fix XSS vulnerabilities of a web application using the output encoding functionality of OWASP ESAPI. Results revealed 3 types of mistakes that programmers made which resulted in them failing to fix the application by removing XSS vulnerabilities. We also identified 16 usability issues of OWASP ESAPI. We identified that some of these usability issues as the reason for mistakes that programmers made. Based on these results, we provided suggestions on how the usability of output encoding APIs should be improved to give a better experience to programmers.