Code:   AccessType GetExtensionAccess(const Extension* extension,
                                 const GURL& url,
                                 int tab_id) {
     bool allowed_script = IsAllowedScript(extension, url, tab_id);
    bool allowed_capture =
        extension->permissions_data()->CanCaptureVisiblePage(tab_id, nullptr);
 
     if (allowed_script && allowed_capture)
       return ALLOWED_SCRIPT_AND_CAPTURE;
    if (allowed_script)
      return ALLOWED_SCRIPT_ONLY;
    if (allowed_capture)
      return ALLOWED_CAPTURE_ONLY;
    return DISALLOWED;
  }

Vulnerability Type: Bypass 
CWE ID: CWE-20
Summary: Insufficient policy enforcement in Extensions API in Google Chrome prior to 67.0.3396.62 allowed an attacker who convinced a user to install a malicious extension to bypass navigation restrictions via a crafted Chrome Extension.
Commit Message: [Extensions] Restrict tabs.captureVisibleTab()

Modify the permissions for tabs.captureVisibleTab(). Instead of just
checking for <all_urls> and assuming its safe, do the following:
- If the page is a "normal" web page (e.g., http/https), allow the
  capture if the extension has activeTab granted or <all_urls>.
- If the page is a file page (file:///), allow the capture if the
  extension has file access *and* either of the <all_urls> or
  activeTab permissions.
- If the page is a chrome:// page, allow the capture only if the
  extension has activeTab granted.

Bug: 810220

Change-Id: I1e2f71281e2f331d641ba0e435df10d66d721304
Reviewed-on: https://chromium-review.googlesource.com/981195
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548891}