I'm submitting a ...

• regression from 1.7.0
• security issue
• issue caused by a new browser version
• other

Current behavior:
By visiting this page https://code.angularjs.org/1.7.8/docs/api/ng/directive/select, section "Using select with ngOptions and setting a default value", all of "Make a choice" options which are clicked on will have the selected="selected" parameter set:
<select name="mySelect" id="mySelect" ng-options="option.name for option in data.availableOptions track by option.id" ng-model="data.selectedOption" class="ng-valid ng-not-empty ng-touched ng-dirty ng-valid-parse"><option label="Option A" value="1" selected="selected">Option A</option><option label="Option B" value="2" selected="selected">Option B</option><option label="Option C" value="3" selected="selected">Option C</option></select>

Expected / new behavior:
Instead of
<option label="Option C" value="3" selected="selected">Option C</option>
could be selected only:
<option label="Option C" value="3" selected>Option C</option>
, and only for the current option which is selected, removing the parameter for the other not selected options.

Minimal reproduction of the problem with instructions:
By visiting this page https://code.angularjs.org/1.7.8/docs/api/ng/directive/select, section "Using select with ngOptions and setting a default value" and the default option is "Option C". When clicking on other options, to the respective option tags will be added the parameter selected="selected".

AngularJS version:
1.7.8

Browser:
Chrome 78.0.3904.97 (64 bit)
Firefox 68.2.0esr (64-bit)
(both running in Debian 9)