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Added notes about XSS when using URIFragments directly #4416

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Merged
merged 2 commits into from
Jul 3, 2025
Merged

Added notes about XSS when using URIFragments directly #4416

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cec4149
Added notes about being mindful about XSS
edler-san Jul 2, 2025
939c90f
Improved clarity of description
edler-san Jul 2, 2025
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9 changes: 8 additions & 1 deletion articles/framework/advanced/advanced-urifu.asciidoc
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,8 @@ public class MyUI extends UI {
}

void enter(String fragment) {
// it is good practice to not use the fragment directly but to sanitize it first
// since it can be set by the user
... initialize the UI ...
}
}
Expand Down Expand Up @@ -155,7 +157,7 @@ public class MyCustomServlet extends VaadinServlet
Writer writer = response.getWriter();
writer.append("<html><body>"+
"<p>Here is some crawlable "+
"content about " + fragment + "</p>");
"content about " + sanitizeHtmlFragment(fragment) + "</p>");

// A list of all crawlable pages
String items[] = {"mercury", "venus",
Expand All @@ -172,6 +174,11 @@ public class MyCustomServlet extends VaadinServlet
} else
super.service(request, response);
}

private String sanitizeHtmlFragment(String s){
// return a String that is safe to use in HTML
... implementation ...
}
}
----

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8 changes: 8 additions & 0 deletions articles/framework/articles/AccessingWebPageAndBrowserInformation.asciidoc
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Expand Up @@ -38,6 +38,14 @@ page.addUriFragmentChangedListener(new UriFragmentChangedListener() {
});
....

Note: HTML is disabled by default in Notifications, but can be enabled with
[methodname]#setHtmlContentAllowed(true)#. When enabled, you can use any HTML
markup in the caption and description of a notification. If it is in any way
possible to get the notification content from user input, you should either
disallow HTML or sanitize the content carefully, as noted in
<<../advanced/advanced-security#advanced.security.sanitizing,"Sanitizing
User Input to Prevent Cross-Site Scripting">>.

You can access client browser details:

[source,java]
Expand Down