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Stored XSS by authenticated backend user with access to upload files

Low severity GitHub Reviewed Published Nov 22, 2020 in octobercms/october • Updated Jan 9, 2023

Package

composer october/backend (Composer)

Affected versions

>= 1.0.319, < 1.0.469

Patched versions

1.0.469

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 octobercms/library@80aab47 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:

Screen Shot 2020-10-10 at 1 47 49 PM

### References - https://github.com/octobercms/october/security/advisories/GHSA-fx3v-553x-3c4q - https://github.com/octobercms/library/commit/80aab47f044a2660aa352450f55137598f362aa4 - https://nvd.nist.gov/vuln/detail/CVE-2020-15249
@LukeTowers LukeTowers published to octobercms/october Nov 22, 2020
Reviewed Nov 23, 2020
Published to the GitHub Advisory Database Nov 23, 2020
Last updated Jan 9, 2023

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

EPSS score

0.050%
(20th percentile)

Weaknesses

CVE ID

CVE-2020-15249

GHSA ID

GHSA-fx3v-553x-3c4q

Source code

No known source code
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