# CVE-2021-47870: GetSimple CMS My SMTP Contact Plugin 1.1.2 - Stored XSS

> Attackers can inject arbitrary client-side code into the administrator's browser via stored XSS in the My SMTP Contact plugin.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 21 Jan 2026
- **Updated:** 12 May 2026
- **Also known as:** GHSA-xcf5-jfw6-6364

## What is CVE-2021-47870?

CVE-2021-47870 is a medium-severity cross-site scripting vulnerability in GetSimple CMS My SMTP Contact Plugin, published on 21 Jan 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

GetSimple CMS My SMTP Contact Plugin 1.1.2 suffers from a Stored Cross-Site Scripting (XSS) vulnerability. The plugin attempts to sanitize user input using htmlspecialchars(), but this can be bypassed by passing dangerous characters as escaped hex bytes. This allows attackers to inject arbitrary client-side code that executes in the administrator's browser when visiting a malicious page.

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

## Which versions are affected by CVE-2021-47870?

It affects 1 product.


Products: Get-Simple Getsimplecms.

## How do I fix CVE-2021-47870?

No fix has been published for CVE-2021-47870 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-47870 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47870 exists.

## Other vulnerabilities in GetSimple CMS My SMTP Contact Plugin

- [CVE-2023-46042](https://insights.sbomify.com/CVE-2023-46042/): Code injection in n/a (critical 9.8)
- [CVE-2020-18191](https://insights.sbomify.com/CVE-2020-18191/): Path traversal in n/a (critical 9.1)
- [CVE-2013-10032](https://insights.sbomify.com/CVE-2013-10032/): GetSimple CMS 3.2.1 Authenticated RCE via Arbitrary PHP File Upload (high 8.7)
- [CVE-2021-47778](https://insights.sbomify.com/CVE-2021-47778/): GetSimple CMS My SMTP Contact Plugin 1.1.2 - PHP Code Injection (high 8.6)
- [CVE-2021-47860](https://insights.sbomify.com/CVE-2021-47860/): GetSimple CMS Custom JS 0.1 - CSRF to XSS to RCE (high 8.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47870 and fix it if it is affected.

What it is: CVE-2021-47870 is a medium-severity cross-site scripting vulnerability in GetSimple CMS My SMTP Contact Plugin, published on 21 Jan 2026. Any signed-in user can exploit it over the network, 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-2021-47870 exists.

Affected product: GetSimple CMS My SMTP Contact Plugin. 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-2021-47870/ (Markdown: https://insights.sbomify.com/CVE-2021-47870/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47870
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47870
- OSV: https://osv.dev/vulnerability/CVE-2021-47870

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47870/
Summaries are generated and may contain mistakes; the official description above is the record.