AUGUST 4, 2026
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Case File

CVE-2021-43776

HIGH · CVSS 7.4 EPSS 0.66% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2021-11-26 · Last synced 2026-08-04

CyberRota Analysis

AI analysis pending.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

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CVE
CVE-2021-43776
Severity
HIGH
CVSS
7.4
EPSS
0.66%

Original NVD Description

Backstage is an open platform for building developer portals. In affected versions the auth-backend plugin 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. This is vulnerability is patched in version `0.4.9` of `@backstage/plugin-auth-backend`.