model/modelstorage.py in trytond 3.2.x before 3.2.10, 3.4.x before 3.4.8, 3.6.x before 3.6.5, and 3.8.x before 3.8.1 allows remote authenticated users to bypass intended access restrictions and write to arbitrary fields via a sequence of records.
http://www.tryton.org/posts/security-release-for-issue5167.html