# CVE-2021-36872: WordPress Popular Posts plugin <= 5.3.3 - Authenticated Persistent Cross-Site Scripting (XSS) vulnerability

> Authenticated attackers can inject persistent scripts via the post_type widget parameter, potentially hijacking user sessions.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Sep 2021
- **Updated:** 28 Apr 2026
- **Also known as:** GHSA-4g64-jfhc-95g2

## What is CVE-2021-36872?

CVE-2021-36872 is a medium-severity cross-site scripting vulnerability in Hector Cabrera WordPress Popular Posts, published on 23 Sep 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Authenticated Persistent Cross-Site Scripting (XSS) vulnerability in WordPress Popular Posts plugin (versions <= 5.3.3). Vulnerable at &widget-wpp[2][post_type].

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

## Which versions are affected by CVE-2021-36872?

It affects 1 product.


Products: Wordpress Popular Posts Project Wordpress Popular Posts.

## How do I fix CVE-2021-36872?

No fix has been published for CVE-2021-36872 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-36872 being exploited?

There is no known exploitation of CVE-2021-36872 in the wild and no public exploit code.

## Other vulnerabilities in Hector Cabrera WordPress Popular Posts

- [CVE-2021-42362](https://insights.sbomify.com/CVE-2021-42362/): WordPress Popular Posts <= 5.3.2 Authenticated Arbitrary File Upload (high 8.8)
- [CVE-2022-43468](https://insights.sbomify.com/CVE-2022-43468/): Business logic in WordPress Popular Posts (high 7.5)
- [CVE-2023-45607](https://insights.sbomify.com/CVE-2023-45607/): WordPress WordPress Popular Posts Plugin <= 6.3.2 is vulnerable to Cross Site Scripting (XSS) (medium 6.5)
- [CVE-2021-20746](https://insights.sbomify.com/CVE-2021-20746/): Cross-site scripting in WordPress Popular Posts (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36872 and fix it if it is affected.

What it is: CVE-2021-36872 is a medium-severity cross-site scripting vulnerability in Hector Cabrera WordPress Popular Posts, published on 23 Sep 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-36872 in the wild and no public exploit code.

Affected product: Hector Cabrera WordPress Popular Posts. 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-2021-36872/ (Markdown: https://insights.sbomify.com/CVE-2021-36872/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36872
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36872
- OSV: https://osv.dev/vulnerability/CVE-2021-36872

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-36872/
Summaries are generated and may contain mistakes; the official description above is the record.