CVE-2020-15249 Stored XSS by authenticated backend user with access to upload files
Authenticated backend users can upload unsanitized SVG files containing JavaScript, leading to stored XSS when victims visit the file URL directly.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-15249?
CVE-2020-15249 is a low-severity cross-site scripting vulnerability in Octobercms October, published on 23 Nov 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. In October CMS from version 1.0.319 and before version 1.0.469, 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. Issue has been patched in Build 469 (v1.0.469) & v1.1.0.
Weakness: CWE-79
Which versions are affected by CVE-2020-15249?
2 open source packages ship an affected version, including october/backend. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
october/backend Packagist | From 1.0.319 | 1.0.469 |
october/backend Packagist | From 1.0.319 | 1.0.469 |
Products include Octobercms October.
How do I fix CVE-2020-15249?
Upgrade october/backend to 1.0.469 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2020-15249 being exploited?
There is no known exploitation of CVE-2020-15249 in the wild and no public exploit code.
Other vulnerabilities in Octobercms October
Sources
Also known as GHSA-fx3v-553x-3c4q.