Shields preventing file uploads after installing most recent update

[allisonphillips]

Description

Shields preventing file uploads in most recent update.

Steps to Reproduce

1. Go to a website like JIRA or GitHub with Brave Shields enabled
2. Attempt to upload an image (I've been attempting Mac OS Screenshot PNGs), either via file picker or drag and drop.

Actual result:

Get an error message along the lines of Something went really wrong, and we can't process that file. Try again. (GitHub)

Expected result:

To be able to upload screenshots and other files, which worked until I installed the most recent Brave version last night.

Reproduces how often:

Every time I try to upload any sort of screenshot. At first I thought it was JIRA being terrible, but I'm experiencing the same behavior with GitHub.

Brave version (brave://version info)

Brave | 0.57.18 Chromium: 71.0.3578.80 (Official Build) (64-bit)
-- | --
Revision | 2ac50e7249fbd55e6f517a28131605c9fb9fe897-refs/branch-heads/3578@{#860}
OS | Mac OS X
JavaScript | V8 7.1.302.28
Flash | (Disabled)
User Agent | Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36
Command Line | /Applications/Brave Browser.app/Contents/MacOS/Brave Browser --disable-domain-reliability --disable-chrome-google-url-tracking-client --no-pings --enable-features=EnableEmojiContextMenu,DesktopPWAWindowing,fill-on-account-select,NewExtensionUpdaterService --disable-features=SharedArrayBuffer,DefaultEnableOopRasterization,VizDisplayCompositor,AutofillSaveCardSignInAfterLocalSave,AutofillServerCommunication,UnifiedConsent --flag-switches-begin --flag-switches-end
Executable Path | /Applications/Brave Browser.app/Contents/MacOS/Brave Browser
Profile Path | /Users/thanx/Library/Application Support/BraveSoftware/Brave-Browser/Default
Variations | c134752e-f685ead32c707b42-dcf7018a411b6d4e-3f4a17dfb7d3b6c2-3f4a17dfd01ab0d3-755bc7553e006338-3f4a17df1a0d11d4-2f9febdf66df3e9d-a85d0b2febeb14fc-3f4a17dfb7e2524c-3f4a17dfb3888d8d-afba0f916c18ba9d-3f4a17df8982496f-3f4a17df61832c80-3f4a17dfcc20827f-77c422c591560a-29acad49041608a-3f4a17df241fff6c-ddf208789853922b-3f4a17df125b7f68-3f4a17df9ca1387e-3f4a17df1c752ce9-1c752ce9776de70c-e0278d3ded9149a9-3f4a17df34d450b1-3f4a17df31362330-3f4a17dfc70841c8-a256700714bdbe54-e8c7a65b8ee5ed19-c3125ea274658432-fa79b94ced7ba060-3f4a17df121ae2bc-65969d679e201a2b-3f4a17df27212adc-27212adc249dd49a-3f4a17df5274eb09-3f4a17dfceff87ec-3f4a17df44827ee5-3f4a17df332a4d9b-8e8e4a2b8f1e27f-3f4a17df345b5b61-3f4a17dfedbcf7c5-ddf1844d77bbdddc-3f4a17df5485fc4d-3f4a17df93731dca-3f4a17df9b4c4257-3f4a17df43f62d3b-3f4a17df4ae380f4-3f4a17df165e16d1-3f4a17df9e5c75f1-30e1b12b6fa07eb4-7282ca762981bcb4-3f4a17df5139837c-3f4a17df4934552d-3f4a17df7f8176d9-3f4a17df6c66bd8d-b204717823a898eb-fc93cf747a5ba892-3f4a17df4ea303a6-3f4a17dfb19465ab-b19465ab6e6e0c7e-3f17a7d895876445-2b71ffe4d92562a9-441539fdfc369826-3f4a17df2b33233e-881ca6c94da5ae82-3f4a17df56302f8c-2f882e7014c5a050-61ceed18cc54eb06-803f8fc4b2612322-8a9180b2ad6d27cc-3e870323df072bba-9a6c5085f56e0452-3f4a17df8576baf1-3f4a17df3038aa2e-3f4a17df51b9b54d-3f4a17df7345ea6-3f4a17df4bc337ce-f483b7fd9a2f4e5b-4bc735aeddf77e2c-63745fe11354da85-522c33b817507c76-3f4a17df494d8760-3f4a17dfbbb8f811-3f4a17df94e68624-803f8fc4cc73f8a1-3f4a17dfb4e8892d-3f4a17df8834fcca-3f4a17df11d91db8-d93a06206204e469-3f4a17dfea0f933d-3f4a17df493ac2c5-803f8fc4

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds? IDK, I'm not going to install those.

Website problems only:

• Does the issue resolve itself when disabling Brave Shields? YES
• Is the issue reproducible on the latest version of Chrome? No

Additional Information

[cndouglas]

Duplicate of #2034

[srirambv]

Closing as dupe. Thanks for linking the issue @liunkae