Hi Felipe
There is a hidden form in Chapter 13 of the Calc guide 7.1, as shown below:
<office:forms form:automatic-focus="false" form:apply-design-mode="false">
<form:form form:name="unnamed0" form:apply-filter="true" form:control-implementation="ooo:com.sun.star.form.component.Form" xlink:href="https://www.altavista.com/web" xlink:type="simple">
<form:properties>
<form:property form:property-name="PropertyChangeNotificationEnabled" office:value-type="boolean" office:boolean-value="true"/>
</form:properties>
</form:form>
</office:forms>
To remove, enable the forms toolbar, open the form navigation window, select the form unnamed0 and delete with context menu.
Regards