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GHSA-fx3v-553x-3c4qlow2.8

Stored XSS by authenticated backend user with access to upload files

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.

Source excerpt · OSV

Affected packages

Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.

october/backend Packagist
Affected rangeRecorded fix
From 1.0.319 before 1.0.469Ecosystem versions1.0.469

Version evidence: OSV · GHSA-fx3v-553x-3c4q

View original version evidence (150 explicit versions)

Original source 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:

Threat assessment:

<img width="1107" alt="Screen Shot 2020-10-10 at 1 47 49 PM" src="https://user-images.githubusercontent.com/7253840/95663787-378f2b80-0aff-11eb-8dfc-b97d162939da.png">

References