Maldoror's Conjecture (Spanish: Conjetura de Maldoror) establishes that, n being the number of possible ways to vandalize an article and m the possible number of official prohibitions to prevent vandalism of an article, it is the case that:

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That is, there will always be ways to vandalize an article that are not expressly gathered as prohibitions in the policies of the Wikipedia.^{[lower-alpha 1]}

In order to replace those inevitable lacunae, it is necessary to resort to common sense. In the case of damage or vandalism to Wikipedia, it is possible to act even though policies do not contemplate the specific case. However, the aim of the policies will have to be the same as the one that guides the action taken on the basis of the common sense.

This conjecture was formulated originally by Maldoror, a retired user of Spanish Wikipedia. It is called a conjecture applying the definition of the concept, since it is a proposal that is presumed real or true, but is based on foundations of an empirical nature and therefore it is not as easily verifiable or testable as a hypothesis.