GHSA-64fm-8hw2-v72w

### Impact KaTeX users who render untrusted mathematical expressions could encounter malicious input using `\edef` that causes a near-infinite loop, despite setting `maxExpand` to avoid such loops. This can be used as an availability attack, where e.g. a client rendering another user's KaTeX input will be unable to use the site due to memory overflow, tying up the main thread, or stack overflow.

### Patches Upgrade to KaTeX v0.16.10 to remove this vulnerability.

### Workarounds Forbid inputs containing the substring `"\\edef"` before passing them to KaTeX. (There is no easy workaround for the auto-render extension.)

### Details KaTeX supports an option named `maxExpand` which prevents infinitely recursive macros from consuming all available memory and/or triggering a stack overflow error. However, what counted as an "expansion" is a single macro expanding to any number of tokens. The expand-and-define TeX command `\edef` can be used to build up an exponential number of tokens using only a linear number of expansions according to this definition, e.g. by repeatedly doubling the previous definition. This has been corrected in KaTeX v0.16.10, where every expanded token in an `\edef` counts as an expansion.

### For more information If you have any questions or comments about this advisory: * Open an issue or security advisory in the [KaTeX repository](https://github.com/KaTeX/KaTeX/) * Email us at [katex-security@mit.edu](mailto:katex-security@mit.edu)