# CVE-2026-81766: Really Simple Security < 9.8.0 - Multisite Subsite Admin+ Arbitrary Plugin Installation via rsp_upgrade_install_plugin

> Subsite administrators can install arbitrary plugins in the network directory, enabling code execution and privilege escalation if the subsite admin menu is enabled.

- **Severity:** Medium 6.6 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-c5mg-rwrq-r34j

## What is CVE-2026-81766?

CVE-2026-81766 is a medium-severity vulnerability in Unknown Really Simple Security, published on 30 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

The Really Simple Security  WordPress plugin before 9.8.0 does not check that the user is allowed to install Really Simple Security  WordPress plugin before 9.8.0 before installing one from a user-supplied URL, allowing an administrator of a subsite on a multisite network to install and execute arbitrary code in the network-shared Really Simple Security  WordPress plugin before 9.8.0 directory, which WordPress otherwise reserves to the network administrator. Exploitation requires the network administrator to have enabled the Really Simple Security  WordPress plugin before 9.8.0 administration menu for subsites, which is not the default.

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2026-81766?


## How do I fix CVE-2026-81766?

No fix has been published for CVE-2026-81766 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81766 being exploited?

There is no known exploitation of CVE-2026-81766 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81766 and fix it if it is affected.

What it is: CVE-2026-81766 is a medium-severity vulnerability in Unknown Really Simple Security, published on 30 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81766 in the wild and no public exploit code.

Affected product: Unknown Really Simple Security. 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-2026-81766/ (Markdown: https://insights.sbomify.com/CVE-2026-81766/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81766
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81766
- OSV: https://osv.dev/vulnerability/CVE-2026-81766

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81766/
Summaries are generated and may contain mistakes; the official description above is the record.