resulted in an alert box appearing on the forum. This attack could also be modified to per"}},{"@type":"Question","name":"How severe is GHSA-5qjq-69w6-fg57?","acceptedAnswer":{"@type":"Answer","text":"GHSA-5qjq-69w6-fg57 has a CVSS score of 10/10, rated CRITICAL. Immediate patching is strongly recommended."}},{"@type":"Question","name":"Which packages are affected by GHSA-5qjq-69w6-fg57?","acceptedAnswer":{"@type":"Answer","text":"GHSA-5qjq-69w6-fg57 affects the following packages: flarum/core (Packagist). Ecosystems affected: Packagist."}},{"@type":"Question","name":"How do I fix GHSA-5qjq-69w6-fg57?","acceptedAnswer":{"@type":"Answer","text":"Update flarum/core to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5qjq-69w6-fg57 is resolved across your whole dependency graph."}},{"@type":"Question","name":"How do I detect GHSA-5qjq-69w6-fg57 in my Packagist dependencies?","acceptedAnswer":{"@type":"Answer","text":"Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match."}},{"@type":"Question","name":"How do I mitigate GHSA-5qjq-69w6-fg57 if there is no patch (or I can't update yet)?","acceptedAnswer":{"@type":"Answer","text":"If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands."}},{"@type":"Question","name":"How does O3 Security protect against GHSA-5qjq-69w6-fg57?","acceptedAnswer":{"@type":"Answer","text":"O3 pinpoints whether GHSA-5qjq-69w6-fg57 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed."}},{"@type":"Question","name":"Is GHSA-5qjq-69w6-fg57 actively exploited in the wild?","acceptedAnswer":{"@type":"Answer","text":"No public exploit code has been indexed for GHSA-5qjq-69w6-fg57 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure."}},{"@type":"Question","name":"What type of vulnerability is GHSA-5qjq-69w6-fg57?","acceptedAnswer":{"@type":"Answer","text":"GHSA-5qjq-69w6-fg57 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure."}},{"@type":"Question","name":"When was GHSA-5qjq-69w6-fg57 published, and has it been updated?","acceptedAnswer":{"@type":"Answer","text":"GHSA-5qjq-69w6-fg57 was published on June 7, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting."}}]}
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🐘 Packagist

GHSA-5qjq-69w6-fg57

CRITICAL

GHSA-5qjq-69w6-fg57 is a critical-severity (CVSS 10) Cross-site Scripting (XSS) vulnerability in flarum/core. O3 Security confirms whether GHSA-5qjq-69w6-fg57 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

XSS vulnerability with translator

Also known asCVE-2021-32671
Published
Jun 7, 2021
Updated
Jul 8, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed

Blast Radius

1 pkg affected
🐘flarum/core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented.

This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as <script>alert('test')</script> resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user, possibly deleting discussions, modifying their settings or profile, or even modifying settings on the Admin panel if the attack was targetted towards a privileged user.

Impact

All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted.

Patches

The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2 using:

composer update --prefer-dist --no-dev -a -W

You can then confirm you run the latest version using:

composer show flarum/core

Workarounds

None.

For more information

For any questions or comments on this vulnerability please visit https://discuss.flarum.org/d/27558.

For support questions create a discussion at https://discuss.flarum.org/t/support.

A reminder that if you ever become aware of a security issue in Flarum, please report it to us privately by emailing [email protected], and we will address it promptly.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistflarum/core≥ 1.0.0&&< 1.0.21.0.2

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update flarum/core to 1.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5qjq-69w6-fg57 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-5qjq-69w6-fg57 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-5qjq-69w6-fg57. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup, such as <script>alert('test')</script> resulted in an alert box appearing on the forum. This attack could also be modified to per
O3 Security · Impact-Aware SCA

Is GHSA-5qjq-69w6-fg57 in your dependencies?

O3 detects GHSA-5qjq-69w6-fg57 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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