The latest beta is mIRC v7.45.721 and can be downloaded from here
Beta 7.45.721 changes:
1.Item 6, http://forums.mirc.com/ubbthreads.php/topics/258505
2.Item 19, http://forums.mirc.com/ubbthreads.php/topics/258233
Beta 7.45.663 changes:
1.Item 13, http://forums.mirc.com/ubbthreads.php/topics/258155
2.Item 14, http://forums.mirc.com/ubbthreads.php/topics/258183
3.Item 15, http://forums.mirc.com/ubbthreads.php/topics/257593
4.Item 9, http://forums.mirc.com/ubbthreads.php/topics/258307
5.Item 16, http://forums.mirc.com/ubbthreads.php/topics/258352
6.Item 17, tested on different Windows versions.
7.Item 18, http://forums.mirc.com/ubbthreads.php/topics/258373
8.Item 3, optimized code.
Beta 7.45.438 changes:
1.Item 1, updated.
2.Item 2, -h should be several times faster.
3.Item 3, also used internally.
4.Item 4, now uses CopyFileEx().
5.Item 5, now uses MoveFileEx().
6.Item 6, needs further testing to ensure no side-effects.
7.Item 7, also makes sure temp file does not already exist.
8.Item 8, settings retained if connected.
9.Item 9, fails if any folder in path cannot be created.
10.Item 10, now uses MoveFileEx().
11.Item 11, required changes to hotlinks and URL catcher.
12.Item 12, adds support for  brackets, eg http://[...].
1.Updated to OpenSSL 1.0.2h library.
2.Fixed /timer -h high resolution timer which was being limited to the
same rate as the -m millisecond timer.
3.Added $samepath(path1,path2) identifier that returns $true/$false
if paths refer to the same file/dir. It resolves relative paths and
converts long/short filenames.
4.Added /copy -f switch to flush copy to disk immediately.
5.Added /rename -f switch to flush rename to disk immediately and -o
switch to allow overwrite of an existing file.
6.Extended $calc() and other identifiers to return up to 12 decimal
digits in floating point calculations.
7.Added $tempfn identifier that returns temporary filename located in
mIRC folder using same method that mIRC uses internally.
8.Fixed Clear History bug that incorrectly cleared channels list
settings while status window was connected to a server.
9.Extended /mkdir to create the full path to the target folder.
10.Changed the way files are replaced during updates to decrease the
potential for file loss eg. lost mirc.ini files in situations such
as crashes, BSODs, and power failures.
11.Changed URL catcher to extract URLs using the same method used by
12.Extended URL hotlink/extract feature to handle IPv6 addresses.
13.Fixed $base() bug with floating point precision.
14.Fixed /hadd not reporting error if UTF-8 conversion results in a
string that is too long.
15.Fixed script error not showing line number for single-line event
16.Added /list -n switch to minimize channels list window.
17.Added resize grip to bottom right of resizable dialogs: channel
central, channel folder, play central, and scripts editor.
18.Fixed regex bug when \K is used in some regex patterns, such as
$regsubex(abcd, /.\K/g, <>).
19.Fixed /drawline -p bug when measuring clipping width for text that
contains tab characters.