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Wed, 28 Oct 2026 22:15:00 +0000
| Type | Values Removed | Values Added |
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| First Time appeared |
W3c
W3c websub |
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| Vendors & Products |
W3c
W3c websub |
Wed, 28 Oct 2026 17:30:00 +0000
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| Metrics |
ssvc
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Tue, 27 Oct 2026 22:45:00 +0000
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| Description | WebSub is a W3C recommendation produced by the Social Web Working Group. In recommendation REC-websub-20180123, the intent-verification protocol requires a subscriber to echo the `hub.challenge` value, also exposed as `hub_challenge` by some frameworks, but does not require safe response media typing or disabled MIME sniffing. An attacker can initiate a subscription to obtain a callback URL and redirect a victim browser to a crafted verification request containing HTML or JavaScript. Subscribers that return the challenge as `text/html` can execute the reflected content in the subscriber origin, using a victim's existing session to read private data or perform actions, exposing `localStorage` or `sessionStorage` and browser permissions granted to that origin. An alternative uses the verification response as an attacker-controlled same-origin script resource to bypass `script-src 'self'`; this can remain possible with `application/octet-stream` when MIME sniffing is allowed. Safe media typing and `X-Content-Type-Options: nosniff` are both needed to address the described scenarios. WebSub Rocks demonstrated reflection, but the advisory does not establish practical impact on that demonstration site. | |
| Title | WebSub: Reflected script execution through intent-verification challenges | |
| Weaknesses | CWE-79 | |
| References |
| |
| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-10-28T16:12:40.129Z
Reserved: 2026-06-04T21:34:34.427Z
Link: CVE-2026-50571
Updated: 2026-10-28T14:35:10.505Z
Status : Deferred
Published: 2026-10-27T23:17:05.687
Modified: 2026-10-28T17:18:30.363
Link: CVE-2026-50571
No data.
OpenCVE Enrichment
Updated: 2026-10-28T21:47:44Z