There is a substantial body of scientific literature on the use of third-party services (TPS) by academics to assist as "publication consultants" in scholarly publishing. TPS provide a wide range of scholarly services to research teams that lack the equipment, skills, motivation, or time to produce a paper without external assistance. While services such as language editing, statistical support, or graphic design are common and often legitimate, some TPS also provide illegitimate services and send unsolicited e-mails (spam) to academics offering these services. Such illegitimate types of TPS have the potential to threaten the integrity of the peer-reviewed scientific literature. In extreme cases, for-profit agencies known as "paper mills" even offer fake scientific publications or authorship slots for sale. The use of such illegitimate services as well as the failure to acknowledge their use is an ethical violation in academic publishing, while the failure to declare support for a TPS can be considered a form of contract fraud. We discuss some literature on TPS, highlight services currently offered by ten of the largest commercial publishers and expect authors to be transparent about the use of these services in their publications. From an ethical/moral (i.e., non-commercial) point of view, it is the responsibility of editors, journals, and publishers, and it should be in their best interest to ensure that illegitimate TPS are identified and prohibited, while publisher-employed TPS should be properly disclosed in their publications.