Mathias Karlsson

@avlidienbrunn · joined 19 Dec 2011

Web security fiddler. Bug bounty bastard. Sometimes I cut shapes.

16 801Followers

611Following

1 394Posts total

74.4KViews on collected posts

Ultimi post

Mathias Karlsson@avlidienbrunn16 Jul

do we still care about xss in void/hidden elements? ff only (visit URL#p): <meta name="description" content="hello" id="p" hidden="until-found" onbeforematch="alert(document.domain)"> <input type="hidden" id="p" hidden="until-found" onbeforematch="alert(document.domain)"> 3.6K views · 64 likes · 3 reposts · 1 replies Open on X →

Mathias Karlsson@avlidienbrunn1 Jul

Some additional context: S3 bucket doesnt have to be public, cdns can have builtin signing (ie bucket/object is private, but cdn has keys to sign). This works if the cdn/middleware forwards query (or if query can be smuggled). 6.1K views · 44 likes · 5 reposts · 1 replies Open on X →

Mathias Karlsson@avlidienbrunn8 May 2025

I made a tool to help test archive (zip/tar) extraction bugs (synk working directory into archive, add path traversals, links, permissions, etc): https://t.co/uEwNUhlTkk 20.2K views · 180 likes · 31 reposts · 2 replies Open on X →

Mathias Karlsson@avlidienbrunn29 Sep 2023

@avlidienbrunn One day I’ll find a use to that payload: </1 hello=“—><img src=“__PARSER__” onerror=console.log(1)>”> Works on some of the parsers 😁 1.8K views · 5 likes · 0 reposts · 1 replies Open on X →

Mathias Karlsson@avlidienbrunn28 Sep 2023

PS. I dont know what that would be useful for, needed this for something else. But finding cases where server-side parse->serialize "made things worse" was fun :D 2.3K views · 4 likes · 0 reposts · 1 replies Open on X →

Mathias Karlsson@avlidienbrunn28 Sep 2023

I made a tool to compare/test server-side HTML parsers: https://t.co/w0DB4LOzM7 . How many "server-side mXSS" can you find? :) 24.7K views · 133 likes · 22 reposts · 4 replies Open on X →

Mathias Karlsson@avlidienbrunn21 Sep 2023

Did you know that JS supports shebang as a comment, and that multiline comments change behaviour depending on what they contain? Is there more?https://t.co/1km558YeSL 15.7K views · 55 likes · 13 reposts · 5 replies Open on X →

Growth & engagement

How the posts we collected actually performed: views and reaction rate post by post, what the audience did with them, and where the follower count goes.

Views per post

15.7K21 Sep

24.7K28 Sep

2.3K

1.8K29 Sep

20.2K8 May

6.1K1 Jul

3.6K16 Jul

Last 7 collected posts, oldest on the left. The scale is logarithmic: one post can outrun the rest a hundred times over.

Engagement rate per post

0.48%21 Sep

0.65%28 Sep

0.22%

0.33%29 Sep

1.06%8 May

0.82%1 Jul

1.91%16 Jul

Reactions — likes, reposts, replies and quotes — divided by views.

What the audience does

Likes51.9%485 in total

Reposts7.9%74 in total

Replies1.6%15 in total

Quotes0.5%5 in total

Bookmarks38.1%356 in total

Share of every reaction we collected for this account. Replies mean argument, reposts mean endorsement, bookmarks mean the post was worth keeping.

The follower curve appears once this account has two daily snapshots — we take one a day, and this one is on its first.

Ultimi post

Growth & engagement

Views per post

Engagement rate per post

What the audience does

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