Perform some very basic validation on names

src/pretix/base/forms/questions.py

@@ -47,7 +47,7 @@ from django.conf import settings
 from django.contrib import messages
 from django.core.exceptions import ValidationError
 from django.core.files.uploadedfile import SimpleUploadedFile
-from django.core.validators import MaxValueValidator, MinValueValidator
+from django.core.validators import MaxValueValidator, MinValueValidator, RegexValidator
 from django.db.models import QuerySet
 from django.forms import Select, widgets
 from django.utils import translation
@@ -187,6 +187,15 @@ class NamePartsFormField(forms.MultiValueField):
         defaults = {
             'widget': self.widget,
             'max_length': kwargs.pop('max_length', None),
+            'validators': [
+                RegexValidator(
+                    # The following characters should never appear in a name anywhere of
+                    # the world. However, they commonly appear in inputs generated by spam
+                    # bots.
+                    r'^[^$€/%§{}<>~]*$',
+                    message=_('Please do not use special characters in names.')
+                )
+            ]
         }
         self.scheme_name = kwargs.pop('scheme')
         self.titles = kwargs.pop('titles')
@@ -207,6 +216,7 @@ class NamePartsFormField(forms.MultiValueField):
             if fname == 'title' and self.scheme_titles:
                 d = dict(defaults)
                 d.pop('max_length', None)
+                d.pop('validators', None)
                 field = forms.ChoiceField(
                     **d,
                     choices=[('', '')] + [(d, d) for d in self.scheme_titles[1]]
@@ -215,6 +225,7 @@ class NamePartsFormField(forms.MultiValueField):
             elif fname == 'salutation':
                 d = dict(defaults)
                 d.pop('max_length', None)
+                d.pop('validators', None)
                 field = forms.ChoiceField(
                     **d,
                     choices=[('', '---')] + PERSON_NAME_SALUTATIONS