Add warning for third-party tools to README
diff --git a/README.md b/README.md
index 33426dc..49a97dc 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,9 @@
 
 ## Third-party tools
 
+> **⚠ WARNING**: the Seedvault developers make no guarantees about external software projects.
+> Please be aware that disclosing your secret recovery key to other software has security risks.
+
 The [Seedvault backup parser](https://github.com/tlambertz/seedvault_backup_parser)
 allows you to decrypt and inspect your backups.
 It can also re-encrypt them.