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1. Embed this notice
   lainy (lain@lain.com)'s status on Friday, 26-May-2023 17:37:09 JST lainy
   I found out how the attack works, it indeed depends on mediaproxy, so if you don't use it you are safe.
   
   You are also safe if you add this code to your nginx.
   
   location ~ ^/(media|proxy) {
   add_header Content-Security-Policy "script-src 'none';";
   
   Updates and fixes incoming, but this will fix the issue right away. There is a certain aspect of social engineering here, it will not just attack you by seeing an image inside pleroma-fe.
   • Polychrome :blabcat: likes this.
   • Embed this notice
     lainy (lain@lain.com)'s status on Friday, 26-May-2023 17:39:35 JST lainy

     in reply to

     • 
     @mint yes, i think so
   • Embed this notice
      (mint@ryona.agency)'s status on Friday, 26-May-2023 17:39:36 JST 

     in reply to
     @lain What about sandbox CSP? Does it have the same effect as script-src 'none'?
     https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/sandbox
   • Embed this notice
     lainy (lain@lain.com)'s status on Friday, 26-May-2023 17:50:14 JST lainy

     in reply to

     • 
     @mint tested it and it indeed fixes it
   • Embed this notice
     lainy (lain@lain.com)'s status on Friday, 26-May-2023 17:53:17 JST lainy

     in reply to

     • 御園はくい
     @hakui mediaproxy is literally killing people
   • Embed this notice
     御園はくい (hakui@tuusin.misono-ya.info)'s status on Friday, 26-May-2023 17:53:18 JST 御園はくい

     in reply to
     @lain no mediaproxy keeps winning :smug1:
   • Embed this notice
     「 Fried Fristi 」 (fristi@akkos.fritu.re)'s status on Friday, 26-May-2023 17:54:22 JST 「 Fried Fristi 」

     in reply to
     @lain yuy am safe :akko_fistup:
     
     Thanks lain :meowHeart:
     lainy likes this.
   • Embed this notice
     lainy (lain@lain.com)'s status on Friday, 26-May-2023 18:12:14 JST lainy

     in reply to

     • 
     • 御shp :blobshp:
     @shpuld @mint it's not in the default, i think you might have it because we had this issue in /media, quick-fixed it via nginx, then also added the fix to pleroma directly, but not fixing it for /proxy because that probably didn't exist yet.
   • Embed this notice
     御shp :blobshp: (shpuld@shpposter.club)'s status on Friday, 26-May-2023 18:12:15 JST 御shp :blobshp:

     in reply to

     • 
     @lain @mint I thought that was in default nginx configs already, it was in mine t least. wonder how it got left out by poast
   • Embed this notice
     御shp :blobshp: (shpuld@shpposter.club)'s status on Friday, 26-May-2023 18:30:39 JST 御shp :blobshp:

     in reply to

     • 
     @lain @mint icic, anyway thanks for investigstion and updates, nice to know that we're safe
     lainy likes this.
   • Embed this notice
     ringo (ringo@noagendasocial.com)'s status on Friday, 26-May-2023 18:32:51 JST ringo

     in reply to

     • ringo

     @lain @ringo@talk-here.com interesting. so it was an injection attack using a malformed or corrupted file, which was actually a base64 encoded script ?

   • Embed this notice
     lainy (lain@lain.com)'s status on Friday, 26-May-2023 18:32:51 JST lainy

     in reply to

     • ringo
     • ringo
     @ringo @ringo no, i'm deliberately unclear here about the exact details because i want to give people a few more hours to add that line to nginx before people with lots of free time start trying to exploit it.
     
     Generally, the average pleroma user should be safe, even if they use mediaproxy. the likelihood that someone who isn't specifically attacked and tricked into clicking something will trigger this exploit is very low.
   • Embed this notice
     Neko McCatface v2023 :verified::makemeneko: (roboneko@bae.st)'s status on Friday, 26-May-2023 20:09:39 JST Neko McCatface v2023 :verified::makemeneko:

     in reply to

     • :apa: スプリットショックウイルス †
     • ✙ dcc :pedomustdie: :phear_slackware:
     @splitshockvirus @dcc @lain @splitshockvirus to prevent remote instances from harvesting metadata on local users who are passively browsing. less leakage is nearly always better
   • Embed this notice
     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Friday, 26-May-2023 20:09:39 JST 翠星石

     in reply to

     • Neko McCatface v2023 :verified::makemeneko:
     @roboneko >to prevent remote instances from harvesting metadata on local users who are passively browsing
     That is why you use Tor Browser - you can browse whatever you want and all the remote instances can see that is that someone is using Tor.
   • Embed this notice
     ✙ dcc :pedomustdie: :phear_slackware: (dcc@annihilation.social)'s status on Friday, 26-May-2023 20:09:40 JST ✙ dcc :pedomustdie: :phear_slackware:

     in reply to

     • :apa: スプリットショックウイルス †
     @splitshockvirus @lain i still dont get why anyone would put that on
   • Embed this notice
     ✙ dcc :pedomustdie: :phear_slackware: (dcc@annihilation.social)'s status on Friday, 26-May-2023 20:09:41 JST ✙ dcc :pedomustdie: :phear_slackware:

     in reply to

     • :apa: スプリットショックウイルス †
     @lain cc @splitshockvirus non media proxy bros we keep winning :dude_smug:
   • Embed this notice
     :apa: スプリットショックウイルス † (splitshockvirus@mstdn.starnix.network)'s status on Friday, 26-May-2023 20:09:41 JST :apa: スプリットショックウイルス †

     in reply to

     • かき@GNUsocialJP
     • ✙ dcc :pedomustdie: :phear_slackware:

     @dcc @lain so it would seem

   • Embed this notice
     feld (feld@bikeshed.party)'s status on Saturday, 27-May-2023 01:25:00 JST feld

     in reply to
     If you use Varnish:
     
     sub vcl_backend_response {
     if (bereq.url ~ "^/proxy/") {
     set beresp.http.Content-Security-Policy = "sandbox";
     }
     }
     
     
     Also clear your MediaProxy cache, because serving the cached variant will have the old header without the CSP rule
     lainy likes this.
   • Embed this notice
     feld (feld@bikeshed.party)'s status on Saturday, 27-May-2023 03:25:10 JST feld

     in reply to

     • clemenceau
     your-domain.com {
     # Your existing configuration here
     
     route /specific-path* {
     header /custom-header "Custom-Header-Value"
     }
     }
     
     
     this was sourced from ChatGPT but looks like something I've done before.
   • Embed this notice
     clemenceau (clemenceau@cutewaifu.enjoyer.network)'s status on Saturday, 27-May-2023 03:25:12 JST clemenceau

     in reply to

     • feld

     @lain @feld thanks for this. Any idea what a similar directive for Caddy be? This is the relevant section of their docs:

     https://caddyserver.com/docs/caddyfile/directives/header