CVE-2026-63135 YOURLS: Stored XSS in referrer statistics chart via crafted Referer header
An attacker can inject malicious JavaScript into YOURLS statistics via a crafted Referer header, leading to code execution and data theft when viewed by admins.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-63135?
CVE-2026-63135 is a high-severity cross-site scripting vulnerability in YOURLS, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-63135?
2 open source packages ship an affected version, including yourls/yourls.
| Package | Affected | Fixed in |
|---|---|---|
yourls/yourls Packagist | From 1.5.1 | 1.10.4 |
yourls/yourls Packagist | From 1.5.1 | 1.10.4 |
How do I fix CVE-2026-63135?
Upgrade yourls/yourls to 1.10.4 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-63135 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63135 exists.
Sources
Also known as GHSA-5h77-88j3-r659.