Pycel through 1.0b30, when operating on an untrusted spreadsheet, allows code execution via a crafted formula in a cell, such as one beginning with the =IF(A1=200, eval("__import__('os').system( substring.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.