This article is a part of our Vulnerability Database (back to index)
Cross-site Scripting occurrences in Opera
URLs using “javascript:” have the protocol removed when pasted into the address bar to protect users from cross-site scripting (XSS) attacks, but in certain circumstances this removal was not performed. This could allow users to be socially engineered to run an XSS attack against themselves. This vulnerability affects Opera for Android versions below 61.0.3076.56532. (2020-12-23, CVE-2020-6159)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>