Visual spoofing in Unicode-based text is anticipated as a severe web security problem in the near future as more and more Unicode-based web documents will be used. In this paper, to detect whether a suspicious Unicode character in a word is visual spoofing or not, the context of the suspicious character is utilized by employing a Bayesian framework. Specifically, two contexts are taken into consideration: simple context and general context. Simple context of a suspicious character is the word where the character exists while general context consists of all homoglyphs of the character within Universal Character Set (UCS). Three decision rules are designed and used jointly for convicting a suspicious character. Preliminary evaluations and user study show that the proposed approach can detect Unicode-based visual spoofing with high effectiveness and efficiency.