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AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
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3DescriptionCVE.org
The SlimStat Analytics plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'User-Agent' header in all versions up to, and including, 5.4.11 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The show_complete_user_agent_tooltip setting must be explicitly enabled by an administrator (disabled by default) for the stored payload to be rendered and executed.
AnalysisAI
Stored cross-site scripting in the SlimStat Analytics WordPress plugin (versions through 5.4.11) allows unauthenticated attackers to inject arbitrary JavaScript via the User-Agent request header, which is persisted unsanitized and later rendered inside the admin Browsers report tooltip. Exploitation requires the non-default 'show_complete_user_agent_tooltip' setting to be enabled by an administrator, after which any admin viewing the affected report executes the attacker's script. No public exploit identified at time of analysis and no EPSS or CISA KEV signal is provided in the supplied data.
Technical ContextAI
SlimStat Analytics is a self-hosted visitor analytics plugin for WordPress maintained by VeronaLabs (CPE cpe:2.3:a:veronalabs:slimstat_analytics). The plugin captures visitor metadata including the HTTP User-Agent header in Browscap::_get_user_agent() and persists it via the Tracker storage layer. Per the 5.4.12 fix, Storage::insertRow() already applied sanitize_text_field()/sanitize_url() on initial insertion, but Storage::updateRow() - invoked on redirect handling (Processor::updateContentType) and AJAX follow-up branches (Ajax::process navigation/outbound/event) - overwrote the row with the raw header, defeating the initial sanitization. The stored value was then concatenated into an admin tooltip span in wp_slimstat_reports::inline_help() (admin/view/wp-slimstat-reports.php line 2099) without output escaping, yielding a CWE-79 stored XSS that fires in the privileged WordPress admin context.
RemediationAI
Vendor-released patch: upgrade SlimStat Analytics to version 5.4.12 (released 2026-05-13), which sanitizes the User-Agent at capture in Browscap::_get_user_agent(), mirrors insertRow()'s sanitize_text_field()/sanitize_url() handling inside Storage::updateRow(), and defangs admin tooltip output via wp_kses_post() in wp_slimstat_reports::inline_help() - see https://github.com/wp-slimstat/wp-slimstat/pull/297 and the Wordfence advisory at https://www.wordfence.com/threat-intel/vulnerabilities/id/0a309bf8-7fe3-4033-993c-3c8dba0f216d. If immediate patching is not possible, the most effective workaround is to ensure the 'show_complete_user_agent_tooltip' option remains disabled (its default state), which prevents rendering of the stored payload at the cost of losing the full User-Agent tooltip in the Browsers report. As an additional compensating control, place the WordPress site behind a WAF rule that strips or rejects HTML/script-bearing User-Agent headers (trade-off: may break legitimate but unusual UAs and analytics fidelity), and audit the wp_slimstat database tables for previously stored payloads containing '<script', 'onerror=', or javascript: before re-enabling the tooltip.
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-32729
GHSA-xvg3-935w-4mv9