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Imagine a link like this: https://example.com/login?vulernable-param=evilcredentialstealingjavascript() https://example.com/login?vulernable-param=evilcredenti
by coderzach 9y ago
Imagine a link like this:
https://example.com/login?vulernable-param=evilcredentialstealingjavascript() https://example.com/login?vulernable-param=evilcredentialste...
If I can convince a user to click that, and then login, I can steal their username, password or anything else. Basically anything they do in that window after clicking that link can be compromised.
- airza 9y agoYes, but that gets passed to the server.
- sbarre 9y agoIt may get logged by the server but if it's designed to be parsed client-side, there may not be any server-side code examining or sanitizing that value before the SPA gets to it.
- ghayes 9y agoWhat about httsp://example.com/login#vulnerable-fragment
- airza 9y agoYes, as i commented elsewhere in this thread that would be fine.
- knowaveragejoe 9y agoWouldn't evilCredntialStealingJavascript() have to be stored on the server in the first place...?
- marcosdumay 9y agoIt needs to be echoed into somewhere on the page. Not necessarily stored on the server.
- thephyber 9y agoNo. DOM-based XSS is when JavaScript running on the client takes data from a "source" (URL parameter, DOM content, cookie, LocalStorage, etc), manipulates it, and then executes it on a "sink" without properly escaping it. Examples of "sources" and "sinks"[1]. I've reported DOM-based XSS on a website that parses user-generated comments for URLs then converts the comment by adding hyperlink markup to the URL. It was done insecurely, so I managed to use combinations of spaces and other HTML attribute delimiters to inject an "onMouseOver" attribute and collect a bounty (about $2000 IIRC). In my case, the payout was large because the data was stored on the server (therefore it was persistent XSS), but with URL fragments, it's possible for the server to never see the content that is passed to the "source". [1] https://docs.google.com/spreadsheets/d/1Mnuqkbs9L-s3QpQtUrOkPx6t5dR3QyQo24kCVYQy7YY/edit https://docs.google.com/spreadsheets/d/1Mnuqkbs9L-s3QpQtUrOk...