The COVID-19 pandemic enabled "quishing", or phishing with malicious QR codes, as they became a convenient go-between for sharing URLs, including malicious ones. To explore the quishing phenomenon, we conducted a 173-participant study where we used a COVID-19 digital passport sign-up trial with a malicious QR code as a pretext. We found that 67 % of the participants were happy to sign-up with their Google or Facebook credentials, 18.5% to create a new account, and only 14.5% to skip on the sign-up. Convenience was the single most cited factor for the willingness to yield participants' credentials. Reluctance of linking personal accounts with new services was the reason for creating a new account or skipping the registration. We also developed a Quishing Awareness Scale (QAS) and found a significant relationship between participants' QR code behavior and their sign-up choices: the ones choosing to sign-up with Facebook scored the lowest while the one choosing to skip the highest on average. We used our results to propose quishing awareness training guidelines and develop and test usable security indicators for warning users about the threat of quishing.