High · CVSS 8.2CVE-2026-63135GHSA-5H77-88J3-R659

YOURLS: Stored XSS in referrer statistics chart via crafted Referer headerCVE-2026-63135

Answer in brief

CVE-2026-63135 records a High severity (CVSS 8.2) vulnerability in YOURLS: Stored XSS in referrer statistics chart via crafted Referer header. The current sources do not mark it as known exploited. The current feed maps yourls/yourls (composer), YOURLS/YOURLS (generic), yourls/yourls (packagist). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 21, 2026Updated Sep 9, 2026Source checked Oct 6, 2026First seen by HOL Aug 21, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.2
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps yourls/yourls (composer), YOURLS/YOURLS (generic), yourls/yourls (packagist). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
yourls/yourlscomposer	>=1.5.1,<=1.10.3	1.10.4
YOURLS/YOURLSgeneric	>= 1.5.1, < 1.10.4	Not reported
yourls/yourlspackagist	>=1.5.1 <1.10.4	1.10.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for yourls/yourls, YOURLS/YOURLS, yourls/yourls.
Review the reported fix. Update yourls/yourls to 1.10.4; yourls/yourls to 1.10.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 21, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.