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Add "<" (<) to the ENCODE list #182
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We have found that browsers (at least Chrome and Firefox) can interpret "/" to close a tag in a HTML comment in a script tag. This means that a malicious attacker could submit a payload like "</script/", prematurely closing the script tag that a Hypernova comment is in, causing the page to crash.
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#167 seems to cover this; it's not all opening tags, it's just |
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Whoops, didn't see that PR. Looking forward to seeing it merged! |
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What?
Also encode the
<character insrc/index.js.Why?
We have found that browsers (at least Chrome and Firefox) can interpret "/" to close a tag in a HTML comment in a script tag.
This means that a malicious attacker could submit a payload like "</script/", get it into hydration data, and prematurely close the script tag that a Hypernova comment is in, causing the page to crash.
Here's a POC (please feel free to inspect and rename it to .html if you believe I'm not giving you malware): whoops.txt
Alternatives
Maybe we should only include
<and drop>from the list if performance is a concern. Replacing the comment-in-script with<!-- {"text": "</script>"} -->correctly runs the script for me in Chrome, so I think escaping only<is acceptable.