Forge Version: 1.12.2-14.23.3.2655
SignPicture Ver: 2.8.1-universal
Wings Horns and Hooves the Ultimate Unicorn Mod Ver(Wings): 1.5.13-1.5.15

Other mods and versions may be affected, these are the versions used to discover the conflict.

Having both of these mods installed results in unexpected behavior in which multiple webpages will be opened in the default browser on map load. In the case of Wings 9 pages can be opened at once without any prompt for confirmation. Disabling chat links in settings does not prevent this. The load time or perhaps the number of mods installed seems to increase the pages opened. When only Wings and SignPicture are installed, 3 web pages open on world start.

Wings does send the URLs that are opened to chat on world start to notify the user of new versions but Wings does NOT open the URLs. This behavior is not observed unless SignPicture is also installed.

This may affect other mods as well but it interestingly does not affect all mods that send URLs to chat. Other mods tested include Buildcraft Ver 7.99.16 and Mr.Crayfish's Furniture Mod Ver 4.2.0 Both mods also post links to chat but neither links are opened if SignPicture is installed.

Despite the fact that only some mods are affected, opening a link without confirmation from the user can be a very dangerous behavior and such unexpected behavior should be prevented.

Including links to latest.log and debug.log.
https://gist.github.com/nitefang/342874de94da3ff93943a60fc6fb83de#file-latest-log

https://gist.github.com/nitefang/342874de94da3ff93943a60fc6fb83de#file-debug-log

This is a strange problem.
We are trying to find out the cause of the problem.

SignPicture has an implementation that may open several browsers, but none of them has any relation.

Probably SignPicture malfunctions the function that allows you to open the page at once without displaying the prompt for confirming the notification of Wings, but since the source code of Wings is not disclosed, details are not known.