Originally published on WardenBit. This Dev.to version keeps the engineering detail and focuses on the attack path, practical impact, and remediation choices teams can act on. Cross-site scripting still gets underestimated in modern web apps. A lot of teams hear "XSS" and think of an old-school alert box, a low-priority frontend bug, or a scanner finding to tidy up later. In ecommerce, that assumption can be expensive. When attacker-controlled input reaches a trusted browser session near account pages, search, support flows, reviews, promo components, or checkout helpers, the issue is not "JavaScript happened to run." The issue is that untrusted code can now operate inside a real customer journey — and that changes everything. That shifts XSS from a UI bug into a trusted-session and conversion-risk issue.…