Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The Snyk Advisor website (https://snyk.io/advisor/) was vulnerable to a stored XSS prior to 28th March 2023. A feature of Snyk Advisor is to display the contents of a scanned package's Readme on its package health page. An attacker could create a package in NPM with an associated markdown README file containing XSS-able HTML tags. Upon Snyk Advisor importing the package, the XSS would run each time an end user browsed to the package's page on Snyk Advisor.
CWE-79 - Cross Site Scripting
Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.