Critical severity · published Jul 27, 2026
CVE-2026-66824
Stored Cross-Site Scripting via Unsafe Capture Tree JSON Embedding
9.2
CVSS
0.4%
EPSS
No
On KEV
Description
A stored cross-site scripting vulnerability existed in the capture tree visualization page. The application embedded the serialized capture tree directly into an inline JavaScript block using the Jinja safe filter.
Because the tree data can contain values derived from captured and potentially attacker-controlled web content, a specially crafted value could prematurely terminate the surrounding <script> element and inject arbitrary HTML or JavaScript. The malicious code would execute in the browser of a user viewing the affected capture tree.
Successful exploitation could allow an attacker to perform actions using the victim’s authenticated session, access information available to the victim, or modify application data within the permissions of the affected user.
The patch removes the JSON data from the HTML document and retrieves it through a dedicated API endpoint. The client then processes the response using response.json(), preventing capture data from being interpreted as executable content within the original page’s HTML or JavaScript context.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LO
lookyloo · lookyloo
through 1.40.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66824
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-66824
github.com
https://github.com/Lookyloo/lookyloo/commit/395187b57322ab311363ccc290c010b180389009
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