What are the disadvantages of the POP protocol?

Can you elaborate on the drawbacks of the POP protocol? Are there any security concerns that users should be aware of? How does it compare to other protocols in terms of efficiency and scalability? What limitations does it pose for large-scale cryptocurrency transactions or for applications requiring high levels of data privacy? Are there any known vulnerabilities that have been exploited in the past? Additionally, how does the POP protocol handle network congestion and latency issues? Understanding these disadvantages can help users make informed decisions when choosing a protocol for their cryptocurrency transactions.