Addresses the primary finding from the May 27 security report (issue #8): the admin widget preview modal (frontend/js/views/widgets.js) and the web player widget renderer (server/player/index.html, 2 sites) loaded user-authored widget HTML into unsandboxed iframes. Same-origin scripts in the widget content could access window.parent.localStorage and exfiltrate the JWT. sandbox="allow-scripts" without allow-same-origin sandboxes the widget into a unique origin: inline scripts (clock, RSS, weather widgets) continue to work, but parent-origin access and same-origin requests are blocked. Verified via Playwright probe against all 6 widget types in the dev DB (clock, rss, social, text, weather, webpage): each renders correctly under the new sandbox and contentDocument access from the parent is blocked (opaque-origin enforcement working). Admin preview unchanged in appearance; player display unchanged. Webpage widget (server/routes/widgets.js) sandbox tightening (drop allow-same-origin) is a separate forthcoming commit - needs test against real embed URLs since some sites rely on same-origin behavior. The sandbox-attribute intersection rule means today's outer-iframe sandbox will cascade and strip allow-same-origin from the webpage widget's inner iframe too; accepted as a narrow cosmetic regression (cookies/localStorage stripped for embedded sites) until the deliberate inner-iframe handling ships. SECURITY.md added with reporting process (GitHub Security Advisories primary, support@bytetinker.net fallback) and scope. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Security Policy
Thanks for taking the time to look at ScreenTinker's security. The project is a one-person open-source effort, so response times reflect that — but reports are taken seriously and handled in good faith.
Reporting a vulnerability
Primary channel — GitHub Security Advisories (preferred):
github.com/screentinker/screentinker/security/advisories/new
GitHub's private advisory flow keeps the report off public issues, lets us draft a fix collaboratively, and produces a CVE if appropriate. Use this unless you have a reason not to.
Fallback — email:
support@bytetinker.net (the maintainer's consultancy inbox; the domain
intentionally differs from screentinker.com — it's the actively-monitored
business address rather than a project-domain alias that might not have
working mail delivery).
Please include:
- A description of the issue and its impact
- Steps to reproduce (the more concrete, the better)
- The commit SHA or release tag you observed it on
- Any proof-of-concept code or payload, if you have one
Response timeline
I aim to acknowledge reports within 3–5 business days and update with a triage assessment within 10 business days. If you haven't heard back in that window, please feel free to nudge — life happens, and reports occasionally slip past.
Fix timelines depend on severity, complexity, and whether the issue is on the hosted instance (screentinker.com) or affects self-hosted deployments too. Critical issues affecting the hosted instance generally get same-week turnaround.
In scope
Reports about the following are welcome and treated as security issues:
- Authentication / session bypass (e.g. JWT forgery, login bypass, privilege escalation)
- Multi-tenancy boundary violations (one workspace's data leaking into another, organization-level isolation breaks)
- XSS in widget rendering or admin UI (e.g. unsandboxed widget content, unescaped user input in dashboard surfaces)
- CSRF on state-changing endpoints
- SQL injection (deviations from parameterized queries are reportable)
- Server-side request forgery (SSRF) via widget URLs, content uploads, webhook handlers, or similar
- Insecure direct object reference (accessing a resource by ID without the proper tenancy gate)
Out of scope
The following are acknowledged but not treated as in-scope security issues for this project:
- Denial of service via excessive resource usage (uploading large files, opening many sockets, etc.) — operational concerns, not security vulnerabilities. Rate limits exist where it matters most.
- Social engineering of the maintainer or other users
- Misconfigurations of self-hosted instances (e.g. exposing the server to the internet without TLS, weak JWT secrets, default passwords). The README documents recommended configuration; deviations are the operator's responsibility.
- Vulnerabilities in third-party dependencies (Express, better-sqlite3, socket.io, etc.) — please report those upstream. If a dependency CVE affects ScreenTinker in a non-obvious way, that's worth flagging here too.
- Reports generated by automated scanners with no manual triage or proof-of-concept (e.g. "your /robots.txt is missing" — not what this project worries about)
Coordinated disclosure
Please wait until a fix has shipped to the hosted instance and origin/main before public disclosure. I'll keep you in the loop on timing and confirm when it's safe to publish. For most issues that window is a few weeks at most; if it stretches longer, that's a signal something is more complex than expected and we'll coordinate.
If you find a critical issue that's being actively exploited (or you believe might be), please say so in the report — I'll prioritize accordingly.
Acknowledgments
If you'd like to be credited for a report, I'm happy to acknowledge you by name in release notes and (when applicable) in the GitHub advisory itself. Let me know in your report whether you'd like credit and how you'd like to be named. Anonymous reports are also welcome — no credit is required.