This is a reference to the Quṣṣāṣ ("storytellers"), members of an institution reportedly established by Muʿāwiya b. Abī Sufyān to promote Umayyad propaganda. Hossein Modarressi cites this reference in his discussion of some of the features of al-Ṣādiq's views on ḥadīth fabrication.
This source is part of the Online Companion to Hossein Modarressi, Text and Interpretation: Imam Jaʿfar al-Ṣādiq and His Legacy in Islamic Law (Harvard University Press, 2022).