Vulnerabilities / Inclusion of cryptocurrency mining script
The presence of this type of libraries is usually a strong indicator that your application has been compromised (which allowed the attacker to add the malicious content).
How to fix
Please note that your web application may have been hacked through another vulnerability that allowed the attacker to insert this library. It’s also possible, but less likely, that an employee with access to the code/server may have changed the application for his/her own profit.