Ensure VM ID is a string in ControllerProofPurpose.

Author: dlongley

CHANGELOG.md

@@ -1,5 +1,11 @@
 # jsonld-signatures ChangeLog
 
+## 11.3.1 - 2024-10-dd
+
+### Fixed
+- Ensure verification method ID is a string when checking controller
+  proof purpose.
+
 ## 11.3.0 - 2024-08-01
 
 ### Changed

lib/purposes/ControllerProofPurpose.js

@@ -70,6 +70,11 @@ module.exports = class ControllerProofPurpose extends ProofPurpose {
       }
 
       const {id: verificationId} = verificationMethod;
+      if(typeof verificationId !== 'string') {
+        throw new Error(
+          `Verification method ID "${verificationMethod.id}" ` +
+          'must be a string.');
+      }
       const {term, _termDefinedByDIDContext} = this;
 
       // if no `controller` specified, use verification method's