---
id: "CVE-2026-121763"
page: "https://infrastack.ai/live/CVE-2026-121763"
kind: "vulnerability"
aliases: ["CVE-2026-121763"]
title: "WordPress Hummingbird plugin: stored XSS through 3.21.2"
severity: "medium"
cvss: 6.5
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "hummingbird-performance", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["hummingbird", "package", "self-hosted", "wordpress"]
not_affected_if: ["plugin-not-installed"]
published_at: "2026-11-09T10:17:07+00:00"
first_seen_at: "2026-11-09T10:25:48+00:00"
updated_at: "2026-11-09T10:26:23+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121763", "first_seen_at": "2026-11-09T10:25:48+00:00"}]
exploit_sources: []
---

# WordPress Hummingbird plugin: stored XSS through 3.21.2

Link for people: https://infrastack.ai/live/CVE-2026-121763 (this .md is for agents)

The Hummingbird performance plugin for WordPress, made by WPMU DEV, does not properly sanitize some input before rendering it in a page. An attacker who can store content in the site can run scripts in other users' browsers.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:hummingbird-performance affected range not listed fixed no fixed version listed

## How to check

- Check the installed Hummingbird version in the WordPress admin plugin list or with `wp plugin get hummingbird-performance --field=version`
- Confirm whether the installed version is `3.21.2` or older

## Fix

- Hummingbird: move to a version later than `3.21.2` (the sources do not name the exact fixed release)

## Timeline

- 2026-11-09T10:25:48+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121763

## From the sources

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in WPMU DEV Hummingbird hummingbird-performance allows Stored XSS.This issue affects Hummingbird: from n/a through 3.21.2.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_