The updated packages fix security vulnerabilities:
An issue was discovered in FlightCrew v0.9.2 and earlier. A NULL pointer dereference occurs in GetRelativePathToNcx() or GetRelativePathsToXhtmlDocuments() when a NULL pointer is passed to xc::XMLUri::isValidURI(). This affects third-party software (not Sigil) that uses FlightCrew as a library. (CVE-2019-13032)
FlightCrew v0.9.2 and older are vulnerable to a directory traversal, allowing attackers to write arbitrary files via a ../ (dot dot slash) in a ZIP archive entry that is mishandled during extraction. (CVE-2019-13241)