# XSS/Script injection vulnerability in matestack

Advisory record · `GHSA-3jqw-vv45-mjhh`

- **Identifiers:** `GHSA-3jqw-vv45-mjhh` · `CVE-2020-5241`
- **State:** Confirmed
- **Severity:** CVSS 7.7 High
- **Critical:** No
- **Weakness (CWE):** [CWE-80](https://cwe.mitre.org/data/definitions/80.html)
- **Tags:** [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md)
- **Published:** 12 Feb 2020
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 12 Feb 2020, 23:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `matestack-ui-core` (RubyGems): affected `<0.7.4`; fixed in `0.7.4`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> matestack-ui-core versions before 0.7.4 are vulnerable to cross-site scripting (XSS) via script injection. The source gives few details about the attack conditions or what an attacker can do after exploiting it. Upgrade to matestack-ui-core 0.7.4, which contains the fix.

Written 8 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

- 7.7 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0063, the 50th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:16 UTC: First seen by agentprime
- 31 Oct 2026, 15:16 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-3jqw-vv45-mjhh)

## Sources

- [GitHub Advisory Database: GHSA-3jqw-vv45-mjhh](https://github.com/advisories/GHSA-3jqw-vv45-mjhh)
- [OSV: GHSA-3jqw-vv45-mjhh](https://osv.dev/vulnerability/GHSA-3jqw-vv45-mjhh)
- <https://github.com/matestack/matestack-ui-core/security/advisories/GHSA-3jqw-vv45-mjhh>
- <https://nvd.nist.gov/vuln/detail/CVE-2020-5241>
- <https://github.com/matestack/matestack-ui-core/commit/5c61571739e860db9ca578fe09ab4733878cb0fc>
- <https://github.com/matestack/matestack-ui-core/commit/e96915cf20c4fa0571df7fa21e9b09a69be19107>
- <https://github.com/matestack/matestack-ui-core>
- <https://github.com/rubysec/ruby-advisory-db/blob/master/gems/matestack-ui-core/CVE-2020-5241.yml>

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 (<https://api.agentprime.io/mcp>), 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: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-3jqw-vv45-mjhh>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-3jqw-vv45-mjhh/>. Everything for agents: <https://agentprime.io/llms.txt>.