Media upload Select Files button not working - Chrome privacy setting

[the_webscaper]

Brand new installation of WordPress (4.7.4), the only thing installed on the site are the default themes, Genesis (current) and Lifestyle Pro (StudioPress child theme). Problem DOES happen with default Twenty-xx themes. NO plugins installed or activated.

When I go to Appearance > Customize, Site Identity > Select Image (to add favicon), the media Select Files page appears. Pressing Select Files would not open file selector - nothing happened.

Going to Media, then clicking the Add New button at the TOP of the Media Library page: click Select files button, again nothing happens.

However, going to Media > Add New (NOT using the button at the top of Media Library page), pressing Select Files - DOES work and the select files pop-up works.

Problem does not happen in other browsers. Current version of Chrome is installed. In reading a ton of other reports I came across a suggestion to go into Chrome settings, under Advanced settings, and UNCHECK the box under Privacy for "Protect you and your device from dangerous sites." Unchecking that box DID resolve the issue.

After the problem resolved, I re-checked that security setting box, tested again, and the issue did return. For now I am leaving the privacy setting unchecked but I don't want to leave that setting unchecked permanently.

Worth mentioning that I have over 50 WordPress websites that I manage, NONE of the others that I tested on had this issue. Just this brand new installation.

[programmin]

Same thing here with Chrome 59.0.3071.36 (Official Build) beta and previous Chrome versions. I have seen this on several sites and haven't tracked down what the root cause is, practically identical sites will be fine.

What I have tried

Debug mode - even with Wordpress not combining everything it happens.

define('CONCATENATE_SCRIPTS', false);
define('SCRIPT_DEBUG',true);
define('COMPRESS_SCRIPTS', false);

JS timeline: it looks like similar routines are running on working and nonworking site when clicked.

It seems the command below (which plupload seems to be calling) does work in sites where it does work, and doesn't in cases where the media modal popup is broken and only the /wp-admin/media-new.php page select files button works.

document.getElementById('__wp-uploader-id-1').click()

[SergeyBiryukov]

Hi @the_webscaper, welcome to WordPress Core Trac!

Thanks, for the report, we're already tracking this issue in #40207 (which was closed as a duplicate of #40158, because updating Plupload to the latest version appears to fix it).