CVE-2018-16874: Input Validation

In Go before 1.10.6 and 1.11.x before 1.11.3, the "go get" command is vulnerable to directory traversal when executed with the import path of a malicious Go package which contains curly braces (both '{' and '}' characters). Specifically, it is only vulnerable in GOPATH mode, but not in module mode (the distinction is documented at https://golang.org/cmd/go/#hdr-Moduleawaregoget). The attacker can cause an arbitrary filesystem write, which can lead to code execution.