# CVE-2026-104477: Showdown through 2.1.0 XSS via unescaped quote in href and src attributes

> Attackers can execute arbitrary scripts via crafted markdown links or images due to unescaped quotes in href and src attributes.

- **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:** No
- **Published:** 2 Oct 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-gc85-xrjc-cv75

## What is CVE-2026-104477?

CVE-2026-104477 is a medium-severity cross-site scripting vulnerability in showdownjs showdown, published on 2 Oct 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 through 2.1.0 contains a cross-site scripting vulnerability in the makehtml link and image subparsers, which fail to escape double quotes in destination URLs placed into href and src attributes. Attackers can craft markdown links or images containing a double quote followed by onerror or onmouseover handlers to execute script when victims view rendered HTML.

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

## Which versions are affected by CVE-2026-104477?


## How do I fix CVE-2026-104477?

No fix has been published for CVE-2026-104477 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104477 being exploited?

There is no known exploitation of CVE-2026-104477 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104477 and fix it if it is affected.

What it is: CVE-2026-104477 is a medium-severity cross-site scripting vulnerability in showdownjs showdown, published on 2 Oct 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: There is no known exploitation of CVE-2026-104477 in the wild and no public exploit code.

Affected product: showdownjs showdown. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-104477/ (Markdown: https://insights.sbomify.com/CVE-2026-104477/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104477
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104477
- OSV: https://osv.dev/vulnerability/CVE-2026-104477

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104477/
Summaries are generated and may contain mistakes; the official description above is the record.