VYPR
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. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. 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.","additionalType":"https://schema.org/SoftwareApplication","sameAs":["https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-32671"]},"keywords":"CVE-2021-32671, critical, CWE-79, Flarum Core","mentions":[{"@type":"SoftwareApplication","name":"Core","applicationCategory":"SecurityApplication","publisher":{"@type":"Organization","name":"Flarum"}}],"isAccessibleForFree":true},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://portal.vyprsec.ai/"},{"@type":"ListItem","position":2,"name":"CVEs","item":"https://portal.vyprsec.ai/cves"},{"@type":"ListItem","position":3,"name":"CVE-2021-32671","item":"https://portal.vyprsec.ai/cves/CVE-2021-32671"}]}]}
Critical severityNVD Advisory· Published Jun 7, 2021· Updated Aug 3, 2024

XSS vulnerability with translator

CVE-2021-32671

Description

Flarum is a forum software for building communities. 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 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. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. 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.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
flarum/corePackagist
>= 1.0.0, < 1.0.21.0.2

Affected products

2

Patches

Vulnerability mechanics

Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

5

News mentions

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