flarum/nicknames extension has display name injection in notification emails (autolink & markdown)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.6 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-30913: 0.18% estimated exploitation activity in the next 30 days; percentile 7.09 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When the flarum/nicknames extension is enabled, a registered user can set their nickname to a string that email clients interpret as a hyperlink. The nickname is inserted verbatim into plain-text notification emails, and recipients may be misled into visiting attacker-controlled domains. Affected package - flarum/nicknames — permissive display name driver that allows special characters; affected since initial release on the 1.x branch Any third-party display name driver that permits special characters would be equally affected. Variants 1. Domain autolink — a nickname such as nasty.com is automatically converted to a clickable hyperlink by virtually all email clients (Gmail, Outlook, Apple Mail, Thunderbird). 2. Markdown link syntax — a nickname such as CLICK is rendered as a clickable hyperlink by email clients that auto-render markdown in plain-text emails (e.g. Apple Mail, Thunderbird). Steps to reproduce Variant 1 (autolink — affects all email clients) 1. Enable…

Published by the source

10 Mar 2026, 00:56 UTC

Last modified by the source

10 Mar 2026, 18:44 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3c4m-j3g4-hh25

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# Patch Next advisory brief: CVE-2026-30913

Advisory: flarum/nicknames extension has display name injection in notification emails (autolink & markdown)
IDs: CVE-2026-30913, GHSA-3c4m-j3g4-hh25
Record: https://patchnext.com/advisories/cve-2026-30913 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flarum/nicknames 1.8.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist flarum/nicknames: affected < 1.8.3; fixed in 1.8.3

## Suggested inspection (read-only)
- Packagist flarum/nicknames: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flarum/nicknames.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3c4m-j3g4-hh25 (GitHub-reviewed advisory GHSA-3c4m-j3g4-hh25 lists affected ranges: Packagist flarum/nicknames >=0 <1.8.3)

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