Mozilla applications are regularly updated for security and stability; however, Mozilla does not provide updates for plug-ins. Plug-ins can cause crashes and hangs and may contain security vulnerabilities. Information on security and stability issues affecting Adobe Flash is available at Adobe's website.
Once you download a plugin you just have that version, no checks are made for upgrades. If you upgrade Firefox (which happens automatically unless you switch it off) any plugins that are not compatible with the new version will be lost.
Plugins are created by third parties, you download them at your own risk. Its your responsibility to determine if the source can be trusted.
