CVE-2021-43776

Description

### Impact This vulnerability allows a malicious actor to trick another user into visiting a vulnerable URL that executes an XSS attack. This attack can potentially allow the attacker to exfiltrate access tokens or other secrets from the user's browser. The default CSP does prevent this attack, but it is expected that some deployments have these policies disabled due to incompatibilities. ### Patches This is vulnerability is patched in version `0.4.9` of `@backstage/plugin-auth-backend`. ### For more information If you have any questions or comments about this advisory: * Open an issue in the [Backstage repository](https://github.com/backstage/backstage) * Visit our chat, linked to in [Backstage README](https://github.com/backstage/backstage)

How to fix CVE-2021-43776

To remediate CVE-2021-43776, upgrade the affected package to a fixed version below.

• —upgrade to 0.4.9 or later

Is CVE-2021-43776 being exploited?

Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 0.4.9

CVSS scores

References (4)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-43776
• PATCHgithub.com/backstage/backstage
• WEBgithub.com/backstage/backstage/security/advisories/GHSA-w7fj-336r-vw49
• WEBgithub.com/backstage/backstage/tree/master/plugins/auth-backend