Is CVE-2026-63135 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-63135 being exploited in the wild.

How severe is CVE-2026-63135?

High severity, with a CVSS score of 8.2, published 21 August 2026.

Which products and versions are affected?

yourls/yourls (Packagist) >= 1.5.1, = 1.5.1, <= 1.10.3.

Is there a fix for CVE-2026-63135?

Yes. yourls/yourls (Packagist): upgrade to 1.10.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-63135 attacked?

It is attacked over the network.

Am I affected by CVE-2026-63135?

Check whether you run yourls/yourls (Packagist) or YOURLS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-63135: YOURLS stored XSS in referrer statistics via crafted Referer header

Q: Is there a fix for CVE-2026-63135?

Yes. yourls/yourls (Packagist): upgrade to 1.10.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-63135 attacked?

It is attacked over the network.

Q: Am I affected by CVE-2026-63135?

Check whether you run yourls/yourls (Packagist) or YOURLS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-63135 · Severity: high · CVSS 8.2 · Published 2026-08-21

YOURLS is a popular URL shortening service that stores HTTP referrer information for analytics. An attacker can inject malicious JavaScript into the referrer data by sending a crafted HTTP header, which is then executed in the browser of administrators or users viewing link statistics. This allows attackers to steal sensitive information like API tokens, modify shortcut destinations, and perform unauthorized actions on behalf of the victim.

Technologies: yourls/yourls (Packagist), YOURLS. Vendors: Packagist, YOURLS.

Quick answers

Is CVE-2026-63135 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-63135 being exploited in the wild.
How severe is CVE-2026-63135?: High severity, with a CVSS score of 8.2, published 21 August 2026.
Which products and versions are affected?: yourls/yourls (Packagist) >= 1.5.1, <= 1.10.3, ECOSYSTEM:introduced=1.5.1,fixed=1.10.4; YOURLS >= 1.5.1, <= 1.10.3.
Is there a fix for CVE-2026-63135?: Yes. yourls/yourls (Packagist): upgrade to 1.10.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-63135 attacked?: It is attacked over the network.
Am I affected by CVE-2026-63135?: Check whether you run yourls/yourls (Packagist) or YOURLS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

yourls/yourls (Packagist): upgrade to 1.10.4 or later
```
composer require yourls/yourls:^1.10.4
```

Technical details

The vulnerability is a stored cross-site scripting (XSS) flaw in YOURLS' referrer statistics page. The root cause lies in the `yourls_google_array_to_data_table()` function in `includes/functions-infos.php`, which manually concatenates referrer domain names into JavaScript array literals without escaping special characters like single quotes, backslashes, and bracket characters. An unauthenticated attacker can craft a URL with a malicious Referer header (e.g., `x',1],['marker',alert(1)],['z.tld`) which survives the insufficient sanitization in `yourls_sanitize_url_safe()` and gets stored in the database. When an authenticated user views the statistics page for that short URL, the payload breaks out of the JavaScript string context and executes arbitrary code in the victim's browser with full access to the authenticated session, allowing token theft, link manipulation, and CSRF attacks. The attack requires user interaction (clicking the stats page) but no authentication from the attacker. Fix: patched in version 1.10.4 by properly escaping JavaScript string literals.

Affected products

YOURLS YOURLS >= 1.5.1, <= 1.10.3

Identifiers

CVE-2026-63135
GHSA-5h77-88j3-r659

Timeline

2026-08-01: disclosed
2026-08-21: advisory
2026-08-21: patched: Fixed in version 1.10.4

References

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