On March 6th 2019, an attack was detected on the PIVX network zerocoin protocol, or zPIV. The linked article provides detailed information about the vulnerability which allows an attacker to fake serials accepted by the network, effectively allowing them to spend zerocoins which were never minted.It also includes information on how it it was detected, where the vulnerability arose from, as well as how it is possible to exploit it, how it was fixed, the steps taken to protect the PIVX ecosystem and how it was disclosed.

https://medium.com/@dev.pivx/report-wrapped-serials-attack-5f4bf7b51701