Fixes #10847
Reported-by: Harry Sintonen
Closes #10848
## Cookie file format
The cookie file format is text based and stores one cookie per line. Lines
- that start with `#` are treated as comments.
+ that start with `#` are treated as comments. An exception is lines that
+ start with `#HttpOnly_`, which is a prefix for cookies that have the
+ `HttpOnly` attribute set.
Each line that specifies a single cookie consists of seven text fields
separated with TAB characters. A valid line must end with a newline