reject missing oauth state in auth return#11881
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Changelog: Reject Bungie OAuth callbacks whose state parameter is missing when no state was stored, closing a login CSRF where an attacker-supplied code could be exchanged.
bhollis
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Jul 13, 2026
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The fix is reasonable, the tests are a bit much. I would've preferred if this were just a one line change.
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The auth return handler checks the state parameter Bungie sends back against the value we saved before redirecting, but when neither is present that check is null against null, so a callback carrying no state passes on any browser that has not stored a state yet. In that case we go on to exchange whatever authorisation code is in the URL, which lets someone hand a victim a return link with their own code and quietly sign them into the attacker's account. This treats a missing stored state as a mismatch, so a code is only exchanged when a state we actually issued comes back, and keeps the existing message for the empty-localStorage case.