Description
This affects the package mpath before 0.8.4. A type confusion vulnerability can lead to a bypass of CVE-2018-16490. In particular, the condition ignoreProperties.indexOf(parts) !== -1 returns -1 if parts is ['__proto__']. This is because the method that has been called if the input is an array is Array.prototype.indexOf() and not String.prototype.indexOf(). They behave differently depending on the type of the input.
Remediation
References
https://github.com/aheckmann/mpath/commit/89402d2880d4ea3518480a8c9847c541f2d824fc
https://snyk.io/vuln/SNYK-JS-MPATH-1577289
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579548