The number for revision ids are unsigned int.
When using html form fields HTMLFloatField/HTMLIntField (or type=int/float) characters - and + are tolerated in the input.
To make this html form field suitable for taking a revision ID, there should be an option to forbid the signs so that -123 or +123 is rejected.
Using min = 0 is not the same as disallow the sign. Using + on oldid= in query is working, but not expected.