overassume
/ˌoʊvərˈæsmjuːm/Definitions
1. verb
to assume or suppose something that is not necessarily true, often based on incomplete or insufficient information
“She overassumed that her boss was unhappy with her work, which led to her being defensive in their meeting.”
2. noun
the act of assuming or supposing something that is not necessarily true
“His overassumption of guilt led to a lengthy investigation, which ultimately cleared his name.”