While on the surface it would seem that there is little danger to your system beyond slower performance (which is enough of a problem) or overheating, any qualified IT support expert will tell you that any unwelcome intrusion in your system must be dealt with. Once inside, the hackers may choose to execute more malicious malware. When Cryptojacking started taking off, many purveyors of Ransomware migrated to this less ostentatious and risky way of making an illicit and illegal buck. As the trends in cyber crime change, so does the hackers' modus operandi. The future will most likely provide more lucrative opportunities, and with the crooks' presence in your computer or network, they are the coiled snake ready to strike.
Varonis, a company that specializes in software for Cybersecurity, lays out an in-depth examination of Cryptojacking HERE.