The user content sandbox can be abused to trick users into opening unexpected documents after several user interactions. The content can be opened with a `blob` origin from the Matrix client, so it is possible for a malicious document to access user messages and secrets.

### Patches

This has been fixed by https://github.com/matrix-org/matrix-react-sdk/pull/5657, which is included in 3.15.0.

### Workarounds

There are no known workarounds.

Affected Packages

npm matrix-react-sdk

Affected versions: 0 (fixed in 3.15.0)

Related CVEs

CVE-2021-21320

Key Information

GHSA ID

GHSA-52mq-6jcv-j79x

Published

March 3, 2021 2:23 AM

Last Modified

April 14, 2021 7:07 PM

CVSS Score

2.5 /10

Primary Ecosystem

npm

Primary Package

matrix-react-sdk

GitHub Reviewed

✓ Yes

Dataset

Last updated: November 26, 2025 6:30 AM

Data from GitHub Advisory Database. This information is provided for research and educational purposes.