tiny-secp256k1 vulnerable to private key extraction when signing a malicious JSON-stringifyable message in bundled environment

tiny-secp256k1 is a tiny secp256k1 native/JS wrapper. Prior to version 1.1.7, a private key can be extracted on signing a malicious JSON-stringifiable object, when global Buffer is the buffer package. This affects only environments where require('buffer') is the NPM buffer package. The Buffer.isBuffer check can be bypassed, resulting in k reuse for different messages, leading to private key extraction over a single invalid message (and a second one for which any message/signature could be taken, e.g. previously known valid one). This issue has been patched in version 1.1.7.