diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..f5700e8
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,17 @@
+# Security Policy
+
+## Supported Versions
+
+`fastsse` is pre-1.0 software. Security fixes are applied to the latest
+released version and the `main` branch. Older pre-1.0 releases are not
+guaranteed to receive backports.
+
+## Reporting a Vulnerability
+
+Please report suspected vulnerabilities privately by opening a GitHub security
+advisory for this repository. If advisories are not available to you, contact
+the maintainers directly before publishing details.
+
+Include the affected package, version, platform, reproduction steps, expected
+impact, and any suggested mitigation. Maintainers will acknowledge valid reports
+as soon as practical and coordinate disclosure after a fix is available.