# CVE-2026-59710: showdown - Stored XSS via Unescaped Table Header ID Attribute Injection

> Attackers can inject malicious scripts via markdown table headers, leading to stored XSS when rendered with default settings.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 Jul 2026
- **Updated:** 7 Jul 2026
- **Also known as:** GHSA-22g5-r2x5-97cx, MINI-2fhh-8m2v-f3vv, MINI-4rmr-2742-mpf5, MINI-h37w-3g9v-9g8q, MINI-qm85-wcc2-329m, MINI-rcx3-rfv5-3223, MINI-vqgr-hvf3-jfmc

## What is CVE-2026-59710?

CVE-2026-59710 is a medium-severity cross-site scripting vulnerability in showdown, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

showdown contains a stored cross-site scripting vulnerability in the parseHeaders function of src/subParsers/makehtml/tables.js that fails to properly escape table header ID attributes. Attackers can inject arbitrary HTML and script-executing SVG elements through double-quote characters in markdown table headers, achieving stored XSS when untrusted markdown is rendered with the default github flavor configuration.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-59710?

2 open source packages ship an affected version, including showdown.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `showdown` | npm | All versions to 2.1.0 | None |
| `showdown` | npm | All versions to 2.1.0 | None |

## How do I fix CVE-2026-59710?

Apply the vendor's patch.

## Is CVE-2026-59710 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59710 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59710 and fix it if it is affected.

What it is: CVE-2026-59710 is a medium-severity cross-site scripting vulnerability in showdown, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59710 exists.

Affected packages and fixed versions:
- showdown (npm): affected all versions up to 2.1.0; no fix listed
- showdown (npm): affected all versions up to 2.1.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59710/ (Markdown: https://insights.sbomify.com/CVE-2026-59710/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59710
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59710
- OSV: https://osv.dev/vulnerability/CVE-2026-59710

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59710/
Summaries are generated and may contain mistakes; the official description above is the record.