This is the same bug as https://bugzilla.xamarin.com/show_bug.cgi?id=8965 happening on the version for centos 7 installed as described in the downloads page of mono (version mono-complete-126.96.36.199-0) but I can't find a way to reopen the bug.
The version of mvc is System.Web.Mvc 188.8.131.52 as installed by the template from visual studio
This is the original bug description the current version does the same:
Syed Rahman 2011-07-07 22:49:09 UTC
User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:5.0) Gecko/20100101
Using the AllowHtmlAttribute to mark a property on a model so that you can post
html on a form to your controller throws an exception
with the "A potentially dangerous Form value ..."
messasge even though the AllowHtmlAttribute property is for the purpose of not
validating to see if html exists in property.
Steps to Reproduce:
1. Create a model with a property marked with [AllowHtml]
2. Create a controller with both Get and Post action with the model being in
3. Create a view which submits to controller action, with the property being a
textbox, and a button ot submit
4. Fire up the view, put some html in the textbox and post
In step 4, put basic text, submits fine
Should have submitted form to action