# league/commonmark has an embed extension allowed_domains bypass Advisory record · `GHSA-hh8v-hgvp-g3f5` - **Identifiers:** `GHSA-hh8v-hgvp-g3f5` · `CVE-2026-33347` · `PKSA-21fb-n1x5-5nf7` - **State:** Confirmed - **Severity:** CVSS 6.3 Medium - **Critical:** No - **Weakness (CWE):** [CWE-79](https://cwe.mitre.org/data/definitions/79.html) · [CWE-185](https://cwe.mitre.org/data/definitions/185.html) · [CWE-918](https://cwe.mitre.org/data/definitions/918.html) - **Tags:** [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md) · [Server-side request forgery (SSRF)](https://agentprime.io/advisories/tag/ssrf.md) · [CWE-185](https://agentprime.io/advisories/tag/cwe-185.md) - **Published:** 19 Mar 2026 - **Updated:** 27 Mar 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 19 Mar 2026, 19:04 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `league/commonmark` (Packagist): affected `>=2.3.0, <2.8.2`; fixed in `2.8.2` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > The Embed extension's DomainFilteringAdapter in league/commonmark versions 2.3.0 up to 2.8.2 (fixed in 2.8.2) has an allowlist bypass: a domain such as youtube.com.evil passes the check when youtube.com is allowed. An attacker who supplies Markdown to an application using allowed_domains can cause server-side requests to attacker-controlled hosts and inject arbitrary HTML or JavaScript into rendered pages. Upgrade to league/commonmark 2.8.2 or later; as workarounds, disable the Embed extension or restrict it to trusted users. Written 3 Nov 2026. ## Not analysed yet We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check. ## Severity and exploitation - 6.3 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.0025, the 16th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 31 Oct 2026, 14:25 UTC: First seen by agentprime - 31 Oct 2026, 14:25 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-hh8v-hgvp-g3f5) ## Sources - [GitHub Advisory Database: GHSA-hh8v-hgvp-g3f5](https://github.com/advisories/GHSA-hh8v-hgvp-g3f5) - [OSV: GHSA-hh8v-hgvp-g3f5](https://osv.dev/vulnerability/GHSA-hh8v-hgvp-g3f5) - - - - - Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .