[BUGFIX] Prevent go back by submit on enter

The first button of type=submit is used by the browser if
the user hint <enter> in a form field. A form should only contains
one submit button, which is fixed now with this patch.

Resolves: #82668
Releases: master, 8.7
Change-Id: I43323dd89be67d18a2818faf11359151223458f1
Reviewed-on: https://review.typo3.org/54282


Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Markus Sommer <markus.sommer@typo3.org>
Tested-by: Markus Sommer <markus.sommer@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>

typo3/sysext/form/Resources/Private/Frontend/Partials/Form/Navigation.html

@@ -4,7 +4,7 @@
 		<div class="btn-group" role="group">
 			<f:if condition="{form.previousPage}">
 				<span class="previous">
-					<f:form.button property="__currentPage" value="{form.previousPage.index}" class="btn btn-cancel" formnovalidate="formnovalidate">{formvh:translateElementProperty(element: form.currentPage, renderingOptionProperty: 'previousButtonLabel')}</f:form.button>
+					<f:form.button property="__currentPage" value="{form.previousPage.index}" type="button" class="btn btn-cancel" formnovalidate="formnovalidate">{formvh:translateElementProperty(element: form.currentPage, renderingOptionProperty: 'previousButtonLabel')}</f:form.button>
 				</span>
 			</f:if>
 			<f:if condition="{form.nextPage}">