Stored XSS in Telerik Report Server Navigation and HTML Links

In Progress® Telerik® Report Server prior to version 12.2.26.1007, a stored cross-site scripting vulnerability in the shared reporting engine allows an authenticated report author to embed javascript: or vbscript: URLs in report navigation actions or HTML text box links. When another user views the malicious report and the embedded navigation is triggered, attacker-controlled script can execute in the web report viewer's origin. In a multi-user Report Server deployment, this can enable privilege escalation by performing actions in a higher-privilege user's authenticated session, including an administrator's session.

Casky was already ahead

This CVE exploits attack patterns that Casky's 323matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Progress Telerik Report Server versions before 12.2.26.1007 contain a stored cross-site scripting (XSS) vulnerability in the shared reporting engine. Authenticated report authors can inject malicious javascript: or vbscript: URLs into report navigation actions and HTML text box links. When other users view these compromised reports and interact with the embedded navigation, attacker-controlled scripts execute within the web report viewer's security context. In multi-tenant or multi-user Report Server deployments, this enables lateral privilege escalation, data theft, and session hijacking. Organizations running vulnerable Telelik Report Server versions with multiple users face significant risk, particularly if reports are shared across privilege boundaries.

Casky's 323 mapped security skills leverage Claude's extended reasoning to detect the attack patterns underlying TA0001 (Initial Access) and TA0043 (Reconnaissance) techniques. Practitioners using Casky would identify suspicious patterns including: detection of javascript: and vbscript: protocol handlers injected into report metadata and navigation configurations; analysis of HTML encoding bypass techniques in text box link fields; identification of report authorship changes coupled with navigation property modifications; and correlation of report access patterns before and after malicious edits. The platform's skill mapping surfaces behavioral indicators such as authenticated users creating reports with embedded script payloads, subsequent report viewing by privileged users, and browser console activity matching injected script execution—enabling security teams to trace the attack chain from initial malicious report creation through exploitation.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

323 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-106155.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

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