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GHSA-hh8v-hgvp-g3f5
No affected components available
Impact
The DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain.
This enables two attack vectors:
- SSRF: The
OscaroteroEmbedAdaptermakes server-side HTTP requests to the embed URL via theembed/embedlibrary. A bypassed domain filter causes the server to make outbound requests to an attacker-controlled host, potentially probing internal services or exfiltrating request metadata. - XSS:
EmbedRendereroutputs the oEmbed response HTML directly into the page with no sanitization. An attacker controlling the bypassed domain can return arbitrary HTML/JavaScript in their oEmbed response, which is rendered verbatim.
Any application using the Embed extension and relying on allowed_domains to restrict domains when processing untrusted Markdown input is affected.
Patches
This has been patched in version 2.8.2. The fix replaces the regex-based domain check with explicit hostname parsing using parse_url(), ensuring exact domain and subdomain matching only.
Workarounds
- Disable the
Embedextension, or restrict its use to trusted users - Provide your own domain-filtering implementation of
EmbedAdapterInterface - Enable a Content Security Policy (CSP) and outbound firewall restrictions
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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