🟡 Allowlist Bypass in setThemeRoot() Enables Cross-Origin CSS Injection (SAP_SE @ui5/webcomponents-base)

Description

setThemeRoot() failed to enforce the sap-allowed-theme-origins allowlist. An attacker-controlled absolute cross-origin URL could be stored and used directly to construct a <link rel=stylesheet> element, even when no <meta name=sap-allowed-theme-origins> tag was present in the document. The same bypass was reachable via the ?sap-themeRoot URL parameter.Exploitation requires attacker-influenced input (e.g., a URL query parameter, tenant configuration, or user-supplied setting) to reach setThemeRoot(). A successful exploit allows an attacker to inject arbitrary CSS into the victim page, enabling:- UI redressing and clickjacking- Phishing overlays- Visual defacement- Limited data exfiltration via CSS attribute selectors targeting predictable DOM content