Vtiger CRM 7.1.0 before Hotfix2 allows uploading files with the extension "php3" in the logo upload field, if the uploaded file is in PNG format and has a size of 150x40. One can put PHP code into the image; PHP code can be executed using "<? ?>" tags, as demonstrated by a CompanyDetailsSave action. This bypasses the bad-file-extensions protection mechanism. It is related to actions/CompanyDetailsSave.php, actions/UpdateCompanyLogo.php, and models/CompanyDetails.php.