Quick answers
- Is CVE-2026-121763 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-121763 being exploited in the wild.
- How severe is CVE-2026-121763?
- Medium severity, with a CVSS score of 6.5, published 9 November 2026.
- Which products and versions are affected?
- WPMU DEV Hummingbird through 3.21.2.
- Is there a fix for CVE-2026-121763?
- Yes: fixed in 4.0.0. Until then: Patchstack has issued a mitigation rule to block attack attempts until the plugin is updated. Sites unable to update immediately should apply the Patchstack protection or restrict subscriber-level access. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-121763 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-121763?
- Check whether you run WPMU DEV Hummingbird at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 4.0.0
Patchstack has issued a mitigation rule to block attack attempts until the plugin is updated. Sites unable to update immediately should apply the Patchstack protection or restrict subscriber-level access.
Technical details
A stored XSS vulnerability in Hummingbird up to version 3.21.2 allows subscribers to inject malicious JavaScript that persists and executes when other users view the affected content. The vulnerability requires a privileged attacker (subscriber role or higher) to craft and submit malicious input, with successful exploitation dependent on user interaction from the victim. The vulnerability was patched in version 4.0.0.
Affected products
- WPMU DEV Hummingbird through 3.21.2
Timeline
- 2026-10-26: disclosed: Reported by mroccon
- 2026-11-07: advisory
- 2026-11-09: other: Published on NVD