# CVE-2026-91999: Apache Sling XSS cross-site scripting in web console plugin

Source: https://junglewise.ai/threats/cve-2026-91999-improper-neutralization-of-input-during-web-page-generation-cross  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-91999 · Severity: medium · CVSS 6.1 · Published 2026-09-23

Apache Sling XSS is a library used to prevent cross-site scripting attacks in web applications. A cross-site scripting vulnerability in the web console plugin allows attackers to inject malicious scripts that execute in users' browsers, potentially stealing session tokens, credentials, or sensitive data. Users should upgrade to version 2.4.12 to resolve the issue.

Technologies: [Apache Sling XSS](https://junglewise.ai/threats/technologies/sling-xss). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-91999 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-91999 being exploited in the wild.

**How severe is CVE-2026-91999?** Medium severity, with a CVSS score of 6.1, published 23 September 2026.

**Which products and versions are affected?** Apache Sling XSS before 2.4.12.

**Is there a fix for CVE-2026-91999?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-91999 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-91999?** Check whether you run Apache Sling XSS 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.

## Technical details

An improper input neutralization vulnerability in the Apache Sling XSS web console plugin allows reflected or stored cross-site scripting (XSS) attacks. The vulnerability stems from inadequate escaping of user-supplied input during HTML generation. An attacker can craft malicious input that bypasses XSS protections, executing arbitrary JavaScript in the context of a victim's browser session.

## Affected products

- Apache Sling XSS before 2.4.12

## Timeline

- 2026-09-23: disclosed

## References

- [https://lists.apache.org/thread/xpcsdkr80ow9p13f7hp3ykrhzky9d4t4](https://lists.apache.org/thread/xpcsdkr80ow9p13f7hp3ykrhzky9d4t4)
- [http://www.openwall.com/lists/oss-security/2026/09/23/14](http://www.openwall.com/lists/oss-security/2026/09/23/14)

## Related threats

- [Apache Sling XSS cross-site scripting in getStyleToken](https://junglewise.ai/threats/cve-2026-123765-improper-neutralization-of-input-during-web-page-generation)
- [Apache Sling XSS XML entity expansion vulnerability](https://junglewise.ai/threats/cve-2026-92001-improper-restriction-of-recursive-entity-references-in-dtds-xml)
- [Apache Sling XSS cross-site scripting vulnerability](https://junglewise.ai/threats/cve-2026-91928-improper-neutralization-of-input-during-web-page-generation-cross)
- [Apache Sling XSS cross-site scripting vulnerability](https://junglewise.ai/threats/cve-2026-91852-improper-neutralization-of-input-during-web-page-generation-cross)
- [Apache Sling XSS reflected XSS in getValidHref()](https://junglewise.ai/threats/cve-2026-73192-an-improper-neutralization-of-input-during-web-page-generation)