Checkbox in iframe - how to check that there is a checkbox and if yes click on it

I am using Java and chromedriver. So far I used the following code to simply click on a button, then a small window popped up and I clicked another button. Interestingly I had not to change to any frame. All worked fine. Here is the code:

// click on button
driver.findElement(By.xpath(hyperlink_take_order)).click();
// a second small window popped up and I clicked another button
driver.findElement(By.xpath("//a[contains(text(),'accept')]")).click();

So far I used xpath to identify the buttons I need to click.

From time to time there is an additional checkbox (sometimes multiple checkboxes) on the second small window which I all need to click on. I tried to find them via xpath but found out that xpath did not work here. All I get in HTML is something like this:

The number in the brackets [] in this case 17232 vary each time, therefore I cannot find a name I can use for the checkbox. I read many articles on stackoverflow and found this peace of code which also did not work.

// click on button
driver.findElement(By.xpath(hyperlink_take_order)).click();
// a second small window popped up         
try
{
driver.switchTo().frame(driver.findElement(By.tagName("iframe")));
System.out.println("change to iframe worked");
List<WebElement> CHECKBOXlist = driver.findElements(By.xpath("//input[@type='checkbox']"));
for(WebElement checkbox : CHECKBOXlist) 
{
System.out.println("there was a checkbox");
System.out.println(checkbox.getAttribute("name"));
checkbox.click();
}
driver.switchTo().defaultContent();
} 
catch (Exception e) 
{
System.out.println("there was no checkbox");
}
driver.findElement(By.xpath("//a[contains(text(),'accept')]")).click();

<div class="md-checkbox product-service md-theme-whitebackground">
<div tabindex="0" class=md-checkbox-container">
<input name="service[17232]" tabindex="-1" id="service_17232" type="checkbox" value ="1" />
</div>
<label class="md-check-label" for="service_17232">This one is blue</label>
</div>

Do you have any idea how I can simply click on all (sometimes multiple) checkboxes on the second small window? Thanks