How severe is GHSA-fx3v-553x-3c4q?

GHSA-fx3v-553x-3c4q has a CVSS score of 2.8/10, rated LOW. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-fx3v-553x-3c4q?

GHSA-fx3v-553x-3c4q affects the following packages: october/backend (Packagist). Ecosystems affected: Packagist.

How do I fix GHSA-fx3v-553x-3c4q?

Update october/backend to 1.0.469 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fx3v-553x-3c4q is resolved across your whole dependency graph.

How do I detect GHSA-fx3v-553x-3c4q in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for october/backend, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-fx3v-553x-3c4q if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is GHSA-fx3v-553x-3c4q actively exploited in the wild?

No public exploit code has been indexed for GHSA-fx3v-553x-3c4q 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.

What is the EPSS score for GHSA-fx3v-553x-3c4q?

GHSA-fx3v-553x-3c4q has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-fx3v-553x-3c4q?

GHSA-fx3v-553x-3c4q 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.

When was GHSA-fx3v-553x-3c4q published, and has it been updated?

GHSA-fx3v-553x-3c4q was published on November 23, 2020 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.

🐘

🐘 Packagist

Not in CISA KEV

LOW severity

Stored XSS by authenticated backend user with access to upload filesGHSA-fx3v-553x-3c4q

LOWFix: octobercms/library@80aab47

GHSA-fx3v-553x-3c4q is a low-severity (CVSS 2.8) Cross-site Scripting (XSS) vulnerability in october/backend. A fix is available for october/backend — see the affected versions and patch details below.

Also known asCVE-2020-15249

Published

Nov 23, 2020

Updated

Jul 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐘october/backend

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

Impact

Backend users with access to upload files were permitted to upload SVG files without any sanitization applied to the uploaded files. Since SVG files support being parsed as HTML by browsers, this means that they could theoretically upload Javascript that would be executed on a path under the website's domain (i.e. /storage/app/media/evil.svg), but they would have to convince their target to visit that location directly in the target's browser as the backend does not display SVGs inline anywhere, SVGs are only displayed as image resources in the backend and are thus unable to be executed.

Patches

Issue has been patched in Build 469 (v1.0.469) & v1.1.0.

Workarounds

Apply https://github.com/octobercms/library/commit/80aab47f044a2660aa352450f55137598f362aa4 to your installation manually if unable to upgrade to Build 469 or v1.1.0.

References

Reported by Hoan Hoang

For more information

If you have any questions or comments about this advisory:

Email us at [email protected]

Threat assessment:

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`october/backend`	≥ 1.0.319&&< 1.0.469	1.0.469`composer require october/backend:^1.0.469`

Affected Products

1 product · 1 configurations

Application

octoberoctobercms

≥ 1.0.319 && < 1.0.469

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for october/backend, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update october/backend to 1.0.469 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fx3v-553x-3c4q is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact Backend users with access to upload files were permitted to upload SVG files without any sanitization applied to the uploaded files. Since SVG files support being parsed as HTML by browsers, this means that they could theoretically upload Javascript that would be executed on a path under the website's domain (i.e. /storage/app/media/evil.svg), but they would have to convince their target to visit that location directly in the target's browser as the backend does not display SVGs inline anywhere, SVGs are only displayed as image resources in the backend and are thus unable to be exec